Also  to the late:
Bill Preston (on left) and Ken Bainbridge (on right)

AUTHOR
Richard Wilson,
Mallinckrodt Research Professor of Physics
Harvard University

CONTENTS
Preface
Foreword
Introduction
Historical Background
A Brief Timeline
The First Harvard Cyclotron
The Second Harvard Cyclotron (1945 – 1955)
The Second Harvard Cyclotron (1955 – 1967)
Proton Radiotherapy - first steps (1962 – 1967)
Who Wanted a Cyclotron?  Who would pay for it? (1963 – 1973)
Proton Radiography and Calcium Measurement
Proton Radiotherapy - the continued work (1975 – 2002)
Other Experiments - Radiation Damage Studies
Other Experiments - Crossections for radionuclide production
Other Experiments - Radionuclide production for medicien and physics
Other non cyclotron experiments in the Cycotron laboratory - the CAT scanner
RIP
Acknowledgements
List of papers published and theses prepared with cyclotron experiments or at the cyclotron laboratory.
50th Anniversary Symposium
A list of downnloadable pictures of cyclotron people
A list of downloadable documents

       This is a brief history of the two cyclotrons built at Harvard University and used between  1935 and 2002.  It is a distinguished history and I, Richard Wilson, am proud to have been a part of it for 47 of these 67 years.   In addition to this web based history, which can be added to at any time, a small hard copy book has been  published by the Harvard university Physics Department and is on sale at Harvard University Press.  In addition there is a  a collection of 800 photographs of the cyclotron, its work, its staff and its place in the community which have been scanned and are available for those who wish.   Of course the Harvard University Archives have papers of many of the participants for the eager historian,  and several hardware items are in the museum of scientific instruments.
      
    The work falls naturally into four  periods.   The first period was that of the construction and use of the first cyclotron from 1935 to 1943 when it was dismantled and taken away for war work.   The second is the construction and initial use of the first cyclotron from 1945 to 1955.  The third period starts with a major upgrade in 1955 and continues until the end of major physics research in 1968, and the fourth period is of intensive use for radiotheapy until final closure in summer 2002.   Production of radioactive isotopes was an important part of the operation of the first cyclotron, but was only incidental in the second cyclotron, although the list of publications shows that it was not unimportant.

       In the first third of the twentieth century  the study of Physics at Harvard for both graduate and undergraduate students continued administratively under the Faculty of Arts and  Sciences.  The space occupied for study and experimentation grew with the construction of  Lyman laboratory in the 1930s, one which  included a research library.  The First World War had  initiated the Department of Physics' role in defense.  Its members had taught military personnel, served in the military, and performed defense research.  The 1930s saw increased interest and investigation into the fields of nuclear science and the beginnings of computer science.  In order  to meet the research needs of its faculty, the Physics Department oversaw construction of a particle  accelerator - a cyclotron.   

       The cyclotron had been invented in Berkeley California in 1929 by Ernest Lawrence and  constructed by Lawrence and his graduate student M. Stanley Livingston.   Although the first nuclear disintegration experiments had been performed by Cockroft and Walton in the  Cavendish laboratory in Cambridge UK, using a rectifier multiplication device which carries their  name,  the cyclotrons proved to be very useful in the 1930s in nuclear disintegration experiments, and following the discovery of artificial radioactivity in 1934 by Joliot-Curie, were used widely in producing a  variety of radioactive nuclei.    Some of these radioactive nuclei were of interest in astrophysics,  some of interest in the study of nuclei themselves and some were useful in nuclear medecine -both in diagnosis and in treatment.     It seemed that every major university should have a  cyclotron and indeed they were built at a number of places - Princeton, MIT (built by M. Stanley Livingston), Cornell (built by Stanley Livingston), Rochester built by S.N. Van Voorhis and Lee  Dubridge and at Yale by E. C. Pollard and H. L. Schultz.   

        Although there was agreement that Harvard University must have a cyclotron, there was less agreement on what such a device was.    This is well illustrated in the following page of cartoons about the Cyclotron.

A Brief Timeline

1937    First cyclotron built at Harvard University for nuclear physics research.
1943    First cycltoron dismantled and sent to Los Alamos
1948    Present synchrocyclotron built with funds from the Office of Naval Research
1949    June 3: First 90 MeV proton beam
1956    Reconstruction at HCL - 160 Me V external beam
1961    May 25: First patient treated at HCL - neurosurgical irradiation
1963    Medical annex and treatment room #1 built with NASA funding
1964    100th patient treated
1966    Treatment charges accepted by Blue Cross/Blue Shield for neurosurgical irradiation
1967    End of Office of Naval Research funding
1971    NCI funds to MEEI and HCL to develop eye treatments
1972     Investigation started on feasibility of proton radiography
1972    Grant obtained from RANN program of NSF for the application of proton radiation to meidcal problems
1973    Studies on potential of using proton activation analysis to determine the calcium content of bone funded by RANN program of NSF
1974    Treatment of first patient with large proton field (11x14 cm)
1975    Treatment of first patient for intraocular malignant melanoma
1977    Treatment room #2 built with NCI and Harvard University funding
1977    1000th patient treated
1979    Eye treatment charges accepted by Blue Cross / Blue Shield
1981    Design study for proton medical facility
1982    2000th patient treated
1985    3000th patient treated
1986    Design studies for proton beam delivery systems
1987    Treatment charges accepted by Blue Cross/Blue Shield for chordomas and chondrosarcomas
1987    4000th patient treated
1989    40th Anniversary of first Harvard proton beam
1990    5000th patient treated
1991    First patient treated in second neurosurgical irradiation program (STAR)
1993    6000th patient treated
1995    Ground Breaking, Northeast Proton Therapy Center (NPTC), Boston
1997    7000th patient treated
1999    8000th patient treated
2001    9000th patient treated
2001    First patient treated at NPTC (November)
2002    April 10th  -The last of 9116 patients was treated at HCL
2002    Sunday, June 2: Cyclotron High-Volltage disconnected by administrative fiat
2002    Monday, June 3: Cyclotron vacuum, cooling, fans shut down
2002    Sunday, June 30: Harvard Cyclotron Laboratory closes.

    In  1936 the construction of the cyclotron begun in the Gordon McKay laboratory, a wooden world war I building on the east side of Oxford Street. The magnet weighed 85 tons and had a 41minch diameter pole tip.  It accelerated protons up to anergy of 12 Mev.  In 1960s a new Engineering Science building was  built on the southern part of the Gordon McKay laboratory and the northern part was dismantled as a fire hazard in 1965 and in 2002 a new building is being finished in its location to house various administrative offices.    

    By 1938 the cyclotron construction was complete and a photograph shows Professor Bainbridge,  left, posing with Professor Street, right, and a graduate student  Dr R. W. Hickman (kneeling).  Dr Hickman wrote his PhD thesis on the Franck-Hertz experiment.  By 1943 Dr Hickman was Lecturer on Physics and Communication Engineering, Assistant Director of the Physics Laboratories (under T. L. Lyman) and Assistant Director of the wartime Radio Research  Laboratory (under F. L. Terman from Stanford).  Later he became Director of the Physics Laboratories until his retirement about 1968.  Another photograph shows a scientist, probably  Professor Street, showing on a blackboard the operation of the accelerating system of the two dees.      The small control room is shown in another photograph.

    The cyclotron had an external beam which slowed and stopped as it passed through the air.   This gives a dramatic picture of the ionization of the air.    The external beam was used for  producing radioactive isotopes for medical purposes.  A photograph shows a technician handling  one of the sources.  The report of the physics department to the university in  1939 states that  radioactive materials supplied to Harvard Medical School, New York  Memorial Hospital and  Massachussets General Hospital in addition to uses for physics at Woods Hole Meteorological Station, MIT physics department and members of Williams College and Purdue University.   It  supported the work of  14 researchers in Harvard departments.    Interestingly, there seemed to  be no interest from the graduate school of engineering after the initial construction.    In 1940 to 1941 the physics department reported that the cyclotron had been in operation for over 1,000 hours.   But the end of this fruitful period, and of the first Harvard Cyclotron was near.

       On September 3^rd 1939 Great Britain and France declared war on Nazi Germany and after the Japanese attack on Pearl Harbor in December 1941 the United States joined the war - now called World war II.   Again many members of the Harvard physics faculty served the war effort in various ways.  Some faculty members, including Professor K.T Bainbridge, had already  been  called to help develop radar at  the radiation laboratory at MIT by E. O. Lawrence on behalf of the NDRC.   But in 1943 after the establishment of Los Alamos that Professor Bainbridge was recruited away to work on the Manhattan Project of the U.S. Army, at Los Alamos, New Mexico to join a highly secret team assembled by Robert Oppenheimer to work on the development of the first atomic bomb. While there it became clear that a cyclotron was needed to measure various nuclear reaction cross sections of interest, and supplement the work already being ably carried out at the Princeton cyclotron.   Discussions began at a high administrative level, and top secret level,  between Harvard President James B. Conant (then away from Cambridge) and General Groves and it was agreed that Harvard would sell the   cyclotron to the US government for $1 with an informal promise of a cyclotron to replace it whenthe war was over. It appears that Paul Buck, then Provost of Harvard University, was not informed of these discussions and he later reported informally how much he agonized over making the decision to send the cyclotron.

       The young scientist Robert R Wilson was sent to Harvard to negotiate the purchase and arrange the transfer.  Since the atomic bomb project was top secret, the purpose of the purchase had to be disguised from those not cleared for secret information.   A medical physicist, Dr Hymer Friedell, accompanied Robert Wilson.  The "cover story" is that the cyclotron was needed for medical treatment of military personnel and it was sent to St Louis to be forwarded to  an "unknown destination" (Los Alamos).  Robert Wilson oversaw the shipment and Dr Hymer  Friedell discusses this story in an excerpt from his  oral history on record with US DOE .  The late Professor John W. DeWire of Cornell told of being dispatched from Los Alamos to Cambridge where he took up residence whilst overseeing the dismantlement and shipping of the cyclotron to Los Alamos via St Louis.

       From the files we show  a photograph of Robert Wilson (center) discussing the issue with  the chairman of the physics department cyclotron committee Percy Bridgman (right) with another unknown man, presumably an associate of Dr Friedell. At one time the picture was believed to be of Dr Friedell himself but his grandson insists it is someone else unknown.  We can find no contemporary account of  exactly what was discussed at the meeting but Bob Wilson who was well known for dramatic (but  essentially accurate) summaries said 30 years later that Bridgman's response was "if you want  it for what you say you want it for you can't have it.  If you want it for what I think you want it for, of course you can have it."

       The source and amount of funds for this first cyclotron is not known to the me.   My memory from discussion with the late Roger Hickman is that the construction cost was about $40,000 of which about $20,000 came from the Rockefeller Foundation which  then funded medical research.    

         Immediately following World  War II, a new cyclotron and nuclear laboratory were   planned.    Professor Bainbridge, still at Los Alamos in the fall of 1945, wrote several letters   (copies are available here1. 2. 3. 4) to colleagues at Harvard to plan a new building instead of Gordon  McKay laboratory.  The letters show that he was, at first,  unsure whether the old cyclotron would   be a new cyclotron would be built.  Wasting no time, in 1945 Harvard University appropriated a sum of $425,000 to expand research facilities in Nuclear Physics.  However, this amount was not enough to fund the construction of both a new cyclotron and a new laboratory.  The U.S. Navy   began a program of funding a program in basic science and through its Office of Naval Research (later a joint program of ONR and AEC administered by ONR) this department of the US   government fulfilled the unwritten obligation of 1943 and offered the funding for the construction of a 160-ton cyclotron.  Harvard provided the funds for the construction of a building to house   both the cyclotron and a connecting laboratory.  The building was originally called the Nuclear   Laboratory and other nuclear facilities such as a betatron were contemplated.    

       We divide the history here into three phases.  The first initial phase encompassed the design and initial construction, operation at 90 Mev and the research up until 1955.    This work is encompassed in this chapter.    The second phase began in 1955 when the energy was raised   to 165 Mev, and the work done on nuclear physics for the next 12 years.   Then we define a third  phase of the 35 years from 1967 to 2002 years during which time the primary work was on   medical treatment.

       Initially the driving force for the new cyclotron was Professor Kenneth Bainbridge.   He   persuaded Robert R Wilson to join the Harvard faculty as Associate Professor of Physics, on hisdeparture from Los Alamos in Summer 1946, and head up the team for the design and  construction.   By agreement, Bob Wilson was to spend the year on leave at Berkeley working  with staff there on cyclotron design while Ken Bainbridge was to keep things going at Cambridge.   In 1947, Bob came to Cambridge but only spent 6 months before taking up a new post as  Professor of Physics and head of the Laboratory for Nuclear Science at Cornell University.   Bob  later commented that one of the facts that influenced him in his departure was being asked to do double teaching  duty to make up for his "goofing off" for a year in Berkeley!    So Ken Bainbridge took over from  him officially in 1946-7 as the Director of the Cyclotron.   But Bob's year had been very  productive.  In addition to establishing the major design parameters, Bob wrote a famous small letter to the American Journal of Radiology which presaged the later medical work.    He was motivated to give some time to medical application as “atonement for involvement in the development of ther bomb at Los Alamos".

         At a conference in Cambridge, UK in September 1946,  which was attended by Richard Wilson, then a  graduate student at Oxford, Professor Bainbridge described  the plans for the new cyclotron.   It was to occupy an empty area  between the old Gordon McKay laboratory on the east side of Oxford Street and the Divinity school on  Divinity Avenue.   The photograph shows this area looking west from the Harvard Divnity School, and shows the old Gordon MacKay laboratory straight ahead, and Palfrey House (still preserved as a historical building but moved  50 yards to the northwest.  Another photograph taken looking north, shows the  cyclotron under construction with Palfrey House behind.   Professor Bainbridge mischievously said, the planned neutron beam would  head straight for the divinity school supposedly sending the occupants to the heavens  prematurely.   At a  group meeting  Mr (later Dr) David Bodansky remembers  an emphastic statement of  Professor Bainbridge.  referring to the proposed medical work which was envisaged to be merely the production of radioactive isotopes,   Bainbridge declared "There will  no rats running around THIS cyclotron."   Such blanket predictions are dangerous and often soon contradicted.   Dr. R.B. "Tex"   Holt, an Assistant Professor  at Harvard had a  wife who  was doing medical research at one of the major Boston hospitals.  She irradiated some of her animals in the area adjacent to the cyclotron soon after the first beam was obtained in 1949.   But this was an isolated study, and the laboratory was  free of the smell of animals until Dr. Raymond (Ray) Kjellberg preformed his experiments on dogs and monkeys in 1963 preparatory to his pioneering neurosurgery treatments.

            In 1948 Professor Norman Ramsey was recruited from Columbia University and became director of the Cyclotron Laboratory.   Lee Davenport, who had the nebulous title of "Coordinator" stayed on and provided an effective transition.  He was given the title of Assciate Director (according to a written record) or Deputy Director (according to Professor Ramsey's memory).   The 1947 - 1948 year was very productive.  The  main components of the cyclotron were  installed.  The 650 ton magnet iron had been fabricated in Pittsburgh, PA, and machined at the "local"  Watertown Arsenal.   It was 23 ft long, 15.5 ft high and 10 ft wide.  The magnet was moved in 14 separate sections, on 3rd or 4th December 1947.  The magnet  was  rigged into place by a special crew of riggers from California who had done much of the rigging  for the cyclotron and other accelerators there.  Part of the magnet yoke was delivered on December 24th 1947 in the snow.  The set of  photographs here shows the magnet assembly by Albert (Pop) Poperell with his special crew from Bigge Drayage Co. of California, as written up in the Boston Globe of January 11th  1948.     The magnet coils, each weighing 37 tons,  of which 30 tons was copper, were wound in the General Electric coil winding shop in Pittsfield,  MA and were the largest coils (14 ft diameter) that could be shipped on the Boston and Maine Railroad to North  Cambridge.  Even then they could not come on the direct Boston and Albany mainline because of inadequate clearances.   It was the clearance on this railroad that was the final arbiter of the  cyclotron energy!    When it became time for the coils to be shipped from Springfield, GE wanted  a responsible Harvard person to "collect" them.   It was arranged that the chairman of the  Department would undertake this task.  The chairman, Professor John H. Van Vleck, was a railroad buff  from his boyhood and gladly agreed provided that he could ride on the footplate of the engine.  Mr W.A. Williams, head of GE Power Transformer division accompanied the train with the first coil, and Van, with Harvard engineer Frank B. Robie accomapnied the second coil. From the vantage point of the footplate Van took several photographs of the ride three of which are shown here.    The vacuum chamber was then installed in the magnet yoke, and the concrete shielding vault was installed outside.   The picture shows the vault  before the sliding concrete slabs were installed to close the western end toward the control room.  A close up shows that the kneeling man is Frank Robie, and engineer who became engineer/designer/building manager for the physics laboratories.

           From then on construction proceeded rapidly.  The dees had to be fastened to the dee stubs, shown here by Mr Richard Wharton, then a young technician who stayed with the cyclotron and the high energy physics program all his working life.   Also an unidentified technician adjusting the oscillator.   The logbook shows that on June 3rd 1949 at 2:03 in the morning, the first beam was obtained.  Present were Norman F. Ramsey, Al. J. Pote, Robert (Bob) Mack, G.P.W. (unknown), Peter Van Heerden, and Lee L. Davenport.   At the celebratory party the champagne cork made a dent in the ceiling plaster board.  This dent was carefully preserved until an unfortunate redecoration sometime about 1980 destroyed the historical dent.   The  first of this set of photographs shows  Professor Ramsey and Associate Director  Lee Davenport posing for the newspapers in the control room on June 10th just before the formal dedication of the cyclotron on June15th 1949. Later photographs in the set show how little it changed over the years.  Provost Paul Buck was chairman of the dedication.  There was a distinguished set of speakers, some of whom shown here, at either the dedication or the subsequent dinner at the Harvard Club.   In addition to Norman F. Ramsey, and Lee L. Davenport, Captain A.L. Pleasant, ONR, (Boston), Alan T. Waterman (ONR Washington), Dr Urner Lidell, H.M.MAcneille, Division of Researtch A.E.C.   The enthusiasm of Davenport and Ramsey was great. O:ne day, after a formal dinner with the President they returned to the cyclotron, in their dinner jackets, to find a leak using a new helium  leak detector that had been delivered that afternoon.   Alas no one else was present to take a  photograph to record the event.  A chart shows the staff during this construction period,  and a  photograph shows many of the staff.    Many stories of this period were told at the 50th anniversary celebration by Norman Ramsey and Lee Davenport.

               The beam for the next 6 years was not at the full design energy but at a reduced energy of 110 Mev, and sometimes as low as 95 Mev,  because of a (temporary) failure to make the oscillator work over the full frequency range and the lack of obvious need for immediate work at a higher energy.   Professor Ramsey,  desirous of pursuing active research work at the cyclotron and even more productive work on  molecular beams (which work later won him the 1989 Nobel prize in physics) ,  arranged for Dr.R.B. Holt (Harvard PhD 1947) to become the  director of the cyclotron from 1950 to 1952.

            Several first rate students obtained their PhD from work at the cyclotron at this time.  David Bodansky, Norton Hintz and Robert Birge were the first.   The photograph shows two of them, Robert Birge and Ann Chamberlain (later Birge),  looking at the counters on which their data was recorded.  At the top of the equipment rack are two binary scalers (counters) based upon the 25 year old Eccles-Jordan circuit, modified by E.B. Lewis at Cambridge in 1935 for nuclear applications, and further developed at Los Alamos by Elmore and Sands.  The student had to note the lamp which showed the state of each binary in this 64 fold scaler, and  perform by slide rule the appropriate arithmetic. Dr Robert Birge, son of the University of California Physics Professor Raymond Birge, was destined later to become a senior research fellow himeself at the University of California at Berkeley, and Ann Chamberlain,  later to become Ann Birge,  became a Professor at Hayward College in California.   Other students include a South African, Dr David Hillman,  who later became a biology Professor in Hebrew  University in Jerusalem.   

           Nikolaas Bloembergen, then a junior fellow in the Society of Fellows,  also tried his hand at using the cyclotron.  He, together with Peter van Heerden,  measured range - energy relationships using the internal cyclotron  beam and compared them to theory.  But Nicholaas was to move on to win the 1981  Nobel Prize in physics  with his paramagnetic maser and his research on non linear optics.   In 1950   Professor Karl Strauch joined Harvard, firstly as a Junior Fellow until 1953 when he became an  Assistant Professor. He worked tirelessly with the cyclotron for the next 10 years.  Shortly there after Walter Selove  was appointed Assistant Professor before moving on in 1956 to the University of Pennsylvania.   

           The  ONR nuclear research contract, of which the cyclotron was the largest part, was the  largest - and at first the only - government contract in the physics department.   As a   consequence the cyclotron laboratory became an employer of graduate students, even of those  whose thesis work would be elsewhere.  Two obtained their PhD before the cyclotron operated.  William Cross worked on "The Conservation of Energy and Momentum in Compton Scattering (PhD 1950) and Leo Lavatelli on "Photoelectric Absorption" in 1951.   Harold I. Ewen was also awarded the  PhD in 1951.  Ewen  with  Professor Purcell,   used  an antenna outside the south face of Lyman Laboratory to measure "Radiation from Galactic Hydrogen at 1420 Megacycles per Second" a direct proof of the existence of interstellar hydrogen.   Another  was Paul Martin, who was awarded the PhD in 1954 for a thesis on "Bound State Problems in Electrodynamics"  and who later became Dean of  Applied Sciences.   He remembers working in the electronic shop.   Other non-cyclotron guests  were also welcomed.  In 1955-1956 Harold Furth was building pulsed high field magnets before  high field superconductors were known - but he was awarded the PhD in 1960 for a thesis on "Magnetic Analysis of K- interactions in nuclei".

           Space for research was scarce so in 1951/2 the nuclear laboratory  building was  extended to the north side to make room for an expanded machine shop and a few offices.   Other appointments of note at this time included  Andreas M. (Andy) Koehler who was appointed at the cyclotron in some capacity that no one remembers, and which capacity Andy very quickly outgrew,  and William (Bill) Preston (Ph.D. Harvard 1936) who remained as director for 20 years.    At the memorial service for Bill, Richard Wilson gave a eulogy outlining his work as a scientific administrator.

       By 1953 it was already becoming apparent that the energy of 95 Mev was too low  for a long term program of nuclear and particle physics.   The pi meson mass had been  determined to be 137 Mev, and to produce pi mesons in appreciable numbers needed an  energy of 300 Mev or more.  In addition, measurements at other cyclotrons (Rochester,  Harwell, Chicago) had shown that protons become polarized by scattering from nuclei andnucleons at energies of 130 Mev and above, but at 90 Mev the polarization is low.   At the  time this was merely an empirical observation, but it can be explained by noting that a   nucleon of energy about 70 - 90 Mev suffers a phase change of 180 degrees as it passes  through a heavy nucleus making the nucleus appear to be opaque (in atomic physics this is the Townsend-Ramsauer effect).  In 1955 for example,   Professor Mme Joliot-Curie increased the planned energy of the cyclotron being built at Orsay near Paris, for this reason.   Before 1953 the way of obtaining an external proton beam was by scattering from   an internal target, with a consequent large loss of intensity.   But in 1953 a scheme was  proposed by James Tuck and Lee Teng to extract the proton beam from the Chicago   cyclotron by a regenerative oscillation scheme.    The theory of this process was expanded   by Le Couteur in Liverpool and used to extract the beam from the Liverpool cyclotron in 1954.   In September 1955 it was decided, therefore, to rebuild the Harvard cyclotron.      This rebuild coincided with the arrival at Harvard of Richard Wilson , the present  historian, as Assistant Professor of Physics.  Several steps were taken simultaneously:

- (1)  The magnet was shimmed to allow cyclotron operation to a higher energy of 165   Mev.

- (2)  The RF oscillator was adjusted so that it would oscillate over the full range of frequencies necessary-

- (3)  A beam extraction system of the LeCouteur design was constructed. 

    As the beam accelerated and occupied a larger diameter orbit in the cyclotron, the protons entered a regenerator (shown in the top left hand picture of this group of five pictures),  consisting of two pieces of high saturation iron, one above and below the orbiting protons at one azimuth.  The regenerator was adjusted to provide an increase of magnetic field with radius that was close to Le Couteur's recipipe as shown in the top right drawing of the same group of five pictures.   Shims were placed at a smaller radius (as shown in the bottom left picture) to compensate for an otherwise incorrect field profile at the smaller radius.  An  oscillation was set upbetween the fall off the main magnetic field and the localized increased field of the regenerator.  The bottom right picture of this group of five shows an extraction channel located at the maximum of the oscillation (at an  azimuth just before the regenerator).   These photographs were  taken after dismantlement of the cyclotron.     The rebuild had a feature unique to Harvard.  It was realized that particles in the regenerator-field fall off oscillation would  all have the same energy in contrast to the distribution of energies of protons striking a target under ordinary conditions.  Two regenerators were constructed.  One, together with the extraction channel,  was used  to extract the beam   completely, and the other to make the monochromatic beam strike a carbon target at the other side of the cyclotron, from which target scattered, polarized, protons were broughtout for experiments.   This is illustarted in the fifth drawing in the bottom center.   Which experimental program was in progress depended upon which   regenerator was inserted into the magnet.   

        We performed a complete set of experiemnts on proton-proton scattering.   Cross section, polarization, depolaration parameter, otation parameter, and two paraemeters R' and A'.    For the spin rotation experiments a spin rotation magnet was built to rotate the spin from the vertical to the horizontal so that the same scattering apparatus could be used as for the depolarization experiments.   Here one of the curious accidents of apparatus building occurred.  We speciffied 3 items:  (i) a magnet (ii) a rectifier (iii) saturable inductors to regulate the current.   All three were built by reputable firms (i)  GE coil winding shop in Medford MA,  (ii) a company in Paterson NJ,  a company in Philadelphia.    All three failed!   Although we got our money back, it was a delay of over six months for the R experiemnst (which were the thesis of Ed Thorndike).   We redid the design for the magnet and the regulated power supply ourselves.    It was interesting because we were one of the first nuclear or high energy groups to use a rectifier system for Dc magnet control rather than an AC motor - DC generator system which had been the norm until that time. 

        Typically the cyclotron was operated by the scientists performing the experiment and at first only he or she would be present on a night shift.  Later it became clear that a second person was important for safety:  the experimenter could fall down, drop a lead brick onto his toe, or otherwise get hurt.  The shift change was a typical time to discuss data.  On one Sunday morning Dr Allan Cormack had been on night shift, Professor Norman Ramsey was coming on day shift, and Professor Richard Wilson came by to discuss the data.  But priorities changed when it was noted that the beam had disappeared, and the magnet current had gone up too high.   The magnet current was regulated by comparing the voltage across a shunt with a reference, and amplifying the difference to run a bidirectional (selsyn) motor.  The motor operated a variable transformer (Variac) which controlled the DC field of the DC generator.   The drive for the variac was a chain and sprocket system, with limit switches.  The system had failed, the limit switches failed to work, the chain had broken and the motor was struggling against the stops.   Dr Cormack and  Professor Ramsey sprang into action.    An instant redesign took place.  An O ring was used instead of the sprocket and chain drive, and two pulleys were made, one each machined by Dr Cormack and Professor Ramsey.  No limit switches were needed because the O ring could slip if the drive went too far.    This system was installed within the hour, and survived for about 20 years before the motor-generator set was replaced by a rectifier system acquired surplus when the Cambridge Electron Accelerator shut down.    Of the three persons present that morning both  Dr Cormack and Dr Ramsey were later awarded the Nobel prize but neither of them for their demonstrated skill as a machinist.

      Assistant Professor Douglas Miller set out to use the polarized neutron beam (obtained by producing neutrons at an angle of 30 degrees from the incident protons) to study neutron proton scattering.   This led to the PhD theses of Russell Hobbie, and Norman Strax.  Later, this neutron beam was improved and was more monochromatic, by allowing the external proton beam to impinge on a liquid deuterium target, by Dr David Measday, a research fellow recruited from Oxford University, who later went to Canada amd became director of the Triumf laboratory.  Other studies included proton-proton inelastic scattering showing collisions from deep shells (Gottschalk) small angle scattering (Steinberg), neutron crossections ( Carpenter); deuteron pickup reactions (Cooper).p-d elastic scattering (Postma) and inelastic scattering (Kuckes).   Particularly notable was the first measurement of bremsstrahlung in proton-proton collisions by Shlaer and Gottshalk.

        The Cyclotron staff, led by Bill Preston and Andy Koehler, continued to be outstanding.   No prhotograph seems to exist of all the staff together, but some photographs have been located of individual machinists, assembly staff and electronic shop staff.  Most of these were transferred to work on high energy experiments at the Cambridge Electron Accelerator and elsewhere as the program shifted its focus.

        Funding was the most difficult task.    Dr Ganz of MGH, pediatrician for Dr Kjellberg's children, suggested to Dr Charles Regan of Massachussets Eye and Ear hopsital that the proton beam was ideal for treating eye tumrs and in particular the heridatary tumor retinablastoma.   Interestingly, we treated only a handful of retinablastomas, but in 2003 they are high on the list of new treatment modalities for NPTC.  Dr Regan put in a proposal to NIH but it was turned down, largely because of inadequate communication between Mass. Eye and Ear and HCL.  Dr Regan mistakenly described the alpha particle beam (not the proton beam) and Dr Preston felt only able to give suport that cost FAS nothing.    Both these defects in the proposal were remedied in a new proposal that was finally successful, that involved Dr Ian Constable and Dr Evangelos Gragoudas.  Nonetheless  medical funding was slow in coming,   so that the physicists  Koehler, Preston and Wilson (called the Biomedical Group in the Harvard archives), started searching.    On the principle of starting with the largest pocket, we approached the medical program of the Atomic Energy Commission which at the time were spending some $4 million a year on proton and alpha radiotherapy at Lawrence Berkeley Laboratory, hoping for a small fraction - perhaps 10% of this sum.    No luck.   But providentially the National Science Foundation started a new program, “Research Appropriate for National Needs”  (RANN).  The cyclotron received two grants for this work.   The first was to adapt the Harvard Cyclotron and for clinical trials.    The second was a pilot study of detecting calcium in the extremities of the body by proton bombardment producing the radioactive potassium K38 and detecting the characteristic 2.16 Mev gamma ray.   In addition fees from the neurosurgery patients brought by Dr Kjellberg continued to arrive.   The treatments by Dr Kjellberg had all used a very localized beam.  It was now necessary to produce a beam with a unifiorm distribution of intensity over a large area and depth.   This was done by using a double scattering technique with an annular aperture to spread the beam with excellent results in horizontal uniformity, and a spinning variable absorber as a range modulator.  This technique was used for 30 years and is still in use at the new accelerator at Massachussets General Hospital and elsewhere.

      In 1972 Drs Suit commenced a program of clinically related radiation biological experiments to assess the RBE value to be employed. These were done by Drs. Robertson of the Harvard School of Public Health, Raju of the Los Alamos Laboratory and E. Hall of Columbia University. These were in vitro  studies. In parallel, a long series of RBE assays were performed on intact tissues of the laboratory mouse by Drs. Urano and then Tepper. The result was that 1.10 was chosen to serve as a generic RBE value, viz  all dose levels and tissues.

    Then in February 1974, the first patient was treated using fractionated dose radiation therapy at the equivalent of about 2 Gy/fraction. This patient was a boy with a posterior pelvic sarcoma. The second was a woman with a skull base sarcoma. This category of tumors now includes some 800 patients with really impressive results. Namely, the 10 year control results are 95% and 45% for chondrosarcoma and chordoma, respectively.  The principal clinicians included Drs  Liebsch, Munzenrider, Austin Seymour, Hug and Suit. The important clinical physicists were Drs Goitein, Verhey and Smith.    In 1975 the first of  2,979 patients was treated for ocular melanoma by a team comprised Drs Evangelos Gragoudas [ophthalmological surgeon of the MEEI], John Munzenrider [radiation oncologist of the MGH] and Michael Goitein [physicist of the MGH].. Dr Goitein developed the first 3D treatment planning software to be implemented in regular clinical work in many parts of the world.  It was first designed for treatment of ocuilar melanoma. He also developed the concept of and brought into clincial practice: DVH, dose volume histogram, DRR [digital reconstructed radiograph], and the display of uncertainty bands around isodose contours. 

    1976 was the year for the start of funding of the first NCI grant for clinical study of proton beam radiation therapy. This funding has been continuous from 1976 to the present. This grant was critical for the conduct of this radiation oncology program. Drs Suit and Goitein served as Co Prini\cipal Investigators to 1976 to 1998 when Dr Jay Loeffler became the PI.

       In 1975 Dr William Preston retired from his positions as director of the cyclotron laboratory and director of the physics laboratories.    The staff now included Dr Robert J. Schneider, Dr Janet Sisterson, Ms Kristen Johnson and Mr Miles Wagner in addition to Andy Koehler as Assitant Director and Bill Preston as Director emeritus.  The management procedure was changed.   The management was vested in the acting director of the laboratory, reviewed by a management  committee chaired by Professor Richard Wilson (other members, Dr S.J Adelstein (Academic Dean HMS), Dr Herman Suit and Dean Richard Leahy) .  This committee reported directly to the Dean of FAS and administratively bypassed the physics department.    By this time the medical program at Harvard Cyclotron laboratory was well under way.   There were three basic prongs.  Each had its peculiarities both in funding and in treatment.    These differences sometimes led to stressful problems.

        One of the reasons for the overall success of the program was the ability of the  Harvard Cyclotron staff to manouvre independently of the rivalries and scientific and political differences of the three groups.   Originally the relationship between the Cyclotron Laboratory and MGH was highly informal.  By informal agreement with Dr William (Bill) Sweet, director of the neurosurgery department at MGH, Harvard Cyclotron was treated as an operating room for purposes of liability and responsibility of the surgeons. All Harvard cyclotron personnel were covered by medical malpractice insurance on the general Harvard University policy.   But the increasing number of patients, and the fact there were three programs of which one, the neurosurgery program, was completely separated (on the hospital side) from the others made a more formal agreement necessary - if only to prevent quarelling between the physicians and surgeons.  This was forced by a stormy interchange in 1977 and made formal and legal. The cyclotron staff also had to be made aware of the demands of patient confidentiality   Harvard University negotiated a one-sided agreement.  MGH was responsible for any liability arising from the treatments, but nonetheless, anyone that on the cyclotron staff had the authority to decide NOT to treat a patient if he felt that the planned treatment was inappropriate.    Fortunately such an eventuality never occurred.

      (1)  Neurosurgical (intercranial) lesions treated by the Neurosurgery department of MGH  Dr Raymond N. Kjellberg and Dr Bernard Kliman, later Dr Chapman)
    Andy Koehler kept meticulous records of these treatments, and we show here a list of the total patients by the end of 1971 and a day to day list in 1976.  
    (2)  Eye tumors treated by Massachusets Eye and Ear Hospital.  (Dr Ian Constable, Dr Evangelos Gragoudas ). The picture shows a typical three-way collaboration  betweem Robert Schneider of HCL, Dr. Evangelos Gragoudas and Dr. Michael Goitein of MGH.
      (3)  Larger tumors treated by the Radiation Medicine Department of MGH. (Dr Herman Suit, Dr Joel Tepper, Dr Michael Goitein, Dr Lynn Verhey)

    We collect here some photographs of the various treatments 

        In the following 27 years each of these groups made major contributions, and each was in its own way essential to the whole program. However from the start  the physicians at  MEEI collaborated very closely with the physicians at the Radiation Medicine Department at MGH and in particular with the physicists (led by Michael Goitein) at MGH.  The software program for 3 dimensional treatment planning which was developed by Michael Goiten was used for both the ocular tumors and the large field tumors as well as being the basis for similar programs at many other medical centers worldwide. In 1981, Professor Richard Wilson went on leave and a change was made.  Dr S. James Adelstein, academic dean in the medical school became Chairman of the management  committee. The reporting was changed to report to the Dean of Applied Sciences instead of the Dean of FAS.  Dr Adelstein remained Chairman for the next 21 years until the shut down in 2002.

        The medical advantantage of all of the treatments followed the point raised by Robert R. Wilson in 1947.     The aim of all radiation treatments is to destroy cancerous and other unwanted tissue, while doing as little damage as possible to the surrounding healthy, and, desired, tissue.   The proton beam succeeds in this for two reasons.  Firstly protons have a well defined range, with a shap increase of ionization at the end of the range first pointed out by Sir William Bragg (the "Bragg peak"). They produce little or no damage beyond the end of the range.  Secondly protons being heavy, scatter less than the elctrons commonly used for radiotherapy. If the tumor or other lesion is small,   (less than 1 cm diameter) as in treatments (1) and (2)  it is comparatively easy to install absorbers so that the protons stop on the lesion.  

    The procedure adopted by Dr Kjellberg (neurosurgeon) was to hold the patient's head rigidly in a sereotactic frame, amd to rotate the patient, seated in a chair, about a vertical axis through the lesion.    The photograph shows Dr Kjellberg adjusting this device with an unidentified nurse looking on.  Dr Kjellberg treated his patients with several beams from different (horizontal) directions, that led to an excellent dose distribution that enabled him to irradiate the pituitary but save the optic nerve.  He varied the dose with the size of the beam in accordance with a graph he prepared of the maximum tolerated dose.  But the treatments were all in one day (a single "fraction").  Dr Kjellberg claimed that the fractionation of the dose would not be halpful because he was treating non-cancerous lesions - a claim that others contested.    In the 1980s other treatments (lasers or improved surgery) proved successful at treating pituitary pobems and Dr Kjellberg switched  to treating other lesions.  He pioneered the treatment of Artero-Venous malformations (AVMs) in which a vein and an atery in the head would stick together.  These lesions, although non cancerous, were often fatal. .  Two years after treatment the lesion vanished.  As Dr Paul  Chapman later commented::  "These cures are commonplace now but seemed miraculous at the time."

    If the lesion is large, as in treatments (3), it is much harder to obtain a uniform dose distribution across the tumor.    The large field arrangement was a simple "double scatterer" techniue that was designed, as was so much, by Andy Koehler.   Firstly the beam impinged on a scatterer to spread the beam.   This resulted in a beam that was non-uniform in intensity across the beam.  Then an absorber was paced in the center of this beam to absorb the higher intensity portion.  Finally there was a second scatterer.  This double scatterer technique produced a remarkably uniform beam distribution.  Then the range was modulated by a set of absorbers on a wheel that rotated during the treatment, allowing the proton beam to stop at various depths in the tumor in turn.   A plastic bolus was machined for each treatment .  This fine tuned the depth of penetration of the beam into the patient and restricted the sidewize extent of the beam.  This system was adopted by proton therpay machines throughout the world.    The final result for the dose distribution acrioss the tumor is was a flat distribution with a sharp fall off at the end.  This is far superior to the distribution obtained with gamma ray sources or with  linear electron accelerators.

         From the beginning of this period onwards it was realized that the Harvard cyclotron was not ideal for the medical work it pioneered.  Although the range of protons in tissue was 10-15 cms, this was not enough to reach all tumors from all directions.   In addition it is far preferable for a cyclotron to be located at the hospital.    Already in 1973 Andy Koehler was thinking about small, cheaper, specialized cyclotron designs.   But it was already realized that the cost of the cyclotron itself was a small part of the total treatment cost.    Work continued.  A picture shows the staff in 1979.   

        Professor Bernard Gottschalk returned to the Harvard Cyclotron Laboratory as a Senior Research Fellow in 1982.   One of the first tasks he undertook was to plan a new accelerator: his choice being a synchrotron because the energy is easily variable.   Although attempts to obtain NIH funds for this new  development failed, his design was useful in the design for the synchrotron at Loma Linda University Medical Center.      That synchrotron was funded in large part by a special grant from the US Departmen of Energy.  This grant was congressionally directed funding from the committee on energy in the US House of Representatives chaired by Representative Lindy Boggs of Louisiana.  Ms Boggs was very sensitive to the need for proton radiotherapy since her daughter, Mayor of Princeton, died of a choroidal melanoma which metastasized.   They became aware of our (Massachussetts Eye and Ear Infirmary, Massachusetts General Hospital and HCL) successful cures too late.   We were asked by a committee staff member whether we would like to be included in the special appropriation, but Harvard University and MGH do not accept congressionally directed ("pork barrel") funds, so that  a hospital based facility in the Boston area had to wait another 10 years.   But the Harvard cyclotron kept going with Andy still as the "hands on" director, shown in this picture with Jason Burns in the control room, and in this picture with the staff in 1989.

        In 1990 after application to NIH design funds were made available for a complete new proton therapy facility - accelerator, beam lines, treatment rooms - the lot.    Professor Michael Goitein, at MGH and Harvard Medical School was the PI of the grant and  undertook the design.   Construction funds were made available in 1994.    The contractor for the fine building was Bechtel, and for the cyclotron and beam lines, IBA of Belgium.    This became the Northeast Proton Therapy Center (NPTC) at MGH built in the exercize yard of the old Charles Street jail.  The building and the first operation of the cyclotron came in on schedule, but reliable operation of the beam, beam transport and gantries was elusive. After much travail,  the first patient was treated in November 2001 and the whole proton therapy program began the switch to NPTC in November 2001, and NPTC picked up the full load by April 2002.

        By 1993 Andy Koehler (shown here in his office) had been with the laboratory 40 years, many of them as acting director or director.  He asked to be relieved of his duties as director, remaining a senior research fellow.  But there was plenty of able talent.  Miles Wagner took  over as director and led the program for the next 9 years.   He led an able staff and like Andy Koehler before him was a "hand on" director, being visible in either the control room or workshop - and on one occasion being available for adice when on vacation in Montana.   In 1999 the Harvard cyclotron had been operating for 50 years.   This was a record for cyclotrons, many of which had shut down as nuclear physics and high energy particle physics developed.   We had already had many major parties.  A "final closing" party in 1967;  another "closing party" in 1970, and a 40th anniversary party.   We had to celebrate once again.  We did so with  a one day symposium followed by a dinner at which Andy Koehler's formal retirement was announced. But With Andy, as with so many loyal Harvard people retirement did not mean stopping work.  

        On Wednesday April 10th 2002 the Harvard cyclotron treated its last patient - the 9,115th.  The patient was a  young boy  with bilateral retinoblastoma - a heriditary cancer of the eye.    Starting when he was 2 months old and continuing till he was 4 months old,   he received 22 irradiations to each eye.  This  photograph of the last patient and his mother were taken at this time.  We anticipate that he will be cured.  The treatment was performed by Dr Mukhai with Nurse Patricia MacManus attending. A total of 2,979 eye tumors have been treated  along with 3,687 neurosurgical lesions and 2,449 large tumors at various sites. A dedicated group of professors, physicians, physicists,  nurses, operators and technicians  from Harvard and MGH attended a small  celebration of this work in the evening.   Dr John Munzenreider and Professor Herman Suit, both from MGH were seen in the control room.   But the sucess of the therapy program is not merely the success of the local sucessor (NPTC) at MGH.   It is the success of the 19 other locations where the HCL/MGH treatments have been copied or are planned.

        The first use of the cyclotron for radiation damage studies came when ATT needed to test their transistors to see whether they would survive in space.  In space there are a number of cosmic ray protons with a peak in the spectrum around 150 Mev.  In 1961 a former graduate student of Professor Robert Pound, Dr Walter Brown, then at Bell Telephone Laboratories in Murray Hill, NJ, brought some of the equipment to be bombarded with 150 Mev protons in the cyclotron.  The equipment survived the test, and so did the equipment on board the Telestar satellite.   NASA also realized that there was a need to understand not only how equipment behaved in the radiation environment of space, but so also was there a need to understand how people behaved.      That was the primary reason that NASA funded the construction of the Medical Annex to the cyclotron.    NASA also funded a special cyclotron with an energy of about 500 Mev in Newport News, Virginia to perform radiation damage studies for satellite communication equipment and components.   But the NASA cyclotron proved too cumbersome for the task and it was shut down in the late 1960s.    Over the years,  NASA directly, and contractors  for NASA, regularly brought equipment to Harvard Cyclotron laboratory for test.  The scientists would typically have the cyclotron to themselves for the whole weekend (when medical work was not being done) with a cyclotron staff member, most recently Mr Ethan Cascio,  to help them.