INTERNATIONAL ACCELERATOR RADIOLOGICAL PROTECTION (IARPE) NEWSLETTER APRIL 92 Vol. 1, No.4 FROM THE EDITOR'S TERMINAL (Nisy Ipe ) ========================================================================= Over the past few years, we have all watched, in amazement, the winds of change blow across the world. Things we thought would never happen have come to pass, walls have crumbled down, barriers broken, and communication channels opened. And in the same vein, can we not cross the international, national, cultural and other barriers that may sometimes divide those of us in the accelerator community? Can we not learn to share our expertise, pool our resources, and reach out and help each other? NEWS FROM BROOKHAVEN (Carl Schopfer ) ========================================================================= A Lab-wide database for Material Safety Data Sheets (MSDS) has been implemented at Brookhaven National Laboratory (BNL). The database allows BNL users and guests to promptly access and retrieve information on chemical properties so that they can work with them safely. Information includes toxicity data, chemical composition, fire and explosion properties, chemical compatibilities with other substances, storage and handling recommendations and disposal requirements and transportation guidance. The database is available for remote access on the Technical Information Division's VAX. To increase speed and data capacity, the system is being migrated this week to a UNIX system. Information is available on-line, and people may receive print copies on request. A facsimile capability will be added in the near future. Wendy Mosca (516-282-4935) of the Safety and Environmental Protection Division may be contacted for further information. POSITION OPEN Contact: Personnel Division 516-282-2113 Brookhaven National Laboratory has an opening for a Safety Engineer. Requires BS (MS preferred) in industrial hygiene, health physics, chemistry or related field, and significant experience in the development and implementation of health and safety programs for assessment and remediation of hazardous waste sites. Requires broad knowledge of regulations including CERCLA and RCRA, and OSHA and NRC requirements. Duties will include coordinating and monitoring health and safety plans, training and general ES&H support to the Office of Environmental Protection. NEWS FROM CERN (Alberto Fasso' ) ========================================================================= The new ISOLDE isotope accelerator on line has been inaugurated. Beam is expected for the end of April, although at present only on a single target station. The ISOLDE facility had been moved from the old 600 MeV synchrocyclotron SC (the first CERN accelerator, now out of operation) to the 1 GeV Booster, the proton injector to the PS proton synchrotron. All equipment was removed from the neutrino beam line, which has been operated at high intensity with 450 GeV protons for about 14 years. The collective dose for the dismantling work amounted to about 200 mSv, to be compared with a planned figure of 450 (but radioactive waste conditioning is not terminated yet). The neutrino cave is now practically empty, but dose rates of about 0.5 mSv/h still prevail due to induced activity in the walls. It is planned to build a new neutrino facility in the same tunnel. Experience gained during decommissioning will be taken into account in designing the new layout. The CERN Director General Carlo Rubbia has agreed that the Radiation Protection Group will take part in a collaboration on external dosimetry studies sponsored by the European Economic Community. Prof. M. Zielczynski, of the Swierk Institute of Atomic Energy in Poland, had joined the RP Group for a few weeks. He and his collaborator Dr. Natalia Golnik from the same Institute gave two seminars on their research in mixed-field dosimetry by means of recombination chambers. One of such type of instruments has already been tried successfully at CERN and it is planned to extend their use in the near future, in parallel with other methods (Tissue-Equivalent Proportional Counter, the CERN multi-detector system CERBERUS, etc.). Another seminar was given by Dr. L. Tommasino, Rome during a short visit to CERN. He presented some recent developments in Solid State Nuclear Track Detectors. NEWS FROM SLAC/SSRL (Nisy Ipe ) ======================================================================== SSRL A new branch line, BL10-1, on the SPEAR beamline 10 wiggler was opened March 12th, 1992. The new line is designed transmit high resolution photons in the soft x-ray region, 100 to 1500 eV (125 to 8 angstroms), using a spherical grating monochromator operating at grazing incidence with a 52 meter radius diffraction grating. The wiggler has a critical energy of 8.7 keV (the energy at which half the power is emitted in photons of higher energy and half at lower energy), and the fan of radiation is 6 mrad wide. BL10-1 has a horizontal acceptance of 2 mrad, collected from one side of the wiggler fan. The first mirror is horizontally deflecting and is used as a low pass filter, absorbing photons above 1500 eV. The mirror is water cooled and designed to absorb up to 2 kW without serious distortion. A second mirror deflects the beam vertically and focuses the beam into the monochromator. The first two mirrors are inside the SPEAR storage ring shielding and the monochromator is in the experimental hall. The beamline, including experimental systems are UHV and directly connected to the SPEAR vacuum system. With two mirrors reflecting the desired photons, first, out of the line of the wiggler and then, out of the plane of the storage ring there was no measurable radiation outside of the vacuum upon opening or during injection of electrons into SPEAR. (Michael Rowen ROWEN@SSRL01) SLAC The following publications published by members of the Radiation Physics Department, over the past year, are available from Bette Reed () of the SLAC Publications Department: S.Mao, J. Liu, and W.R. Nelson, ``Using the EGS4 Code to Determine Radiation Sources along Beam Lines at Electron Accelerators'', submitted to the Proceedings of the American Nuclear Society Topical Meeting, New Horizons in Radiation Protection and Shielding, Pasco, Washington, April 26-May 1, 1992, SLAC PUB-5723, January 1992. N.E.Ipe, and J.C.Liu, ``Shielding and Radiation Protection at the SSRL 3 GeV Injector'', submitted to the Proceedings of the American Nuclear Society Topical Meeting, New Horizons in Radiation Protection and Shielding, Pasco, Washington, April 26-May 1, 1992, SLAC PUB-5714, December 1991. R.C. McCall, `` Beta-Ray Exposure From Work on Components With Induced Activity From High Energy Accelerators'' internal publication SLAC TN 91-12, October 1991. N.E.Ipe, and J.C.Liu, ``High Level Dosimetry at the Stanford Linear Accelerator Center'', submitted to the Proceedings of IRPA8, Montreal, Quebec, Canada, May 17-22, 1992, SLAC PUB-5714, October 1991. J.C.Liu, T.M.Jenkins, R.C.McCall and N.E.Ipe, ``Neutron Dosimetry at SLAC: Neutron Sources and Instrumentation'', internal publication, SLAC TN-91-3, October 1991. N.E.Ipe, J.C.Liu, B.R.Buddemier, C.J.Miles, and R.C.Yoder, ``A Comparison of the Neutron Response of CR-39 Made by Different Manufacturers'', presented at the Seventh Symposium on Neutron Dosimetry, Berlin, Germany, October 13-18, 1991, SLAC PUB-5655 September 1991. (To be published in Proceedings) N.E.Ipe, ``Radiological Aspects of the SSRL 3 GeV Injector'', internal publication, SLAC TN-91-11, September 1991. The following publications may be requested from individual authors: M.Conti, A.Del Guerra, D.Mazzei, P.Russo, W.Bencivelli, E.Bertolucci, A.Messinoe, V.Rosso, A. Stefanini, U.Bottigli, P. Randaccio, and W.R. Nelson, ``Use of the EGS4 Monte Carlo Code to Evaluate the Response of HgI2 and CdTe Detectors for Photons in the Diagnostic Energy Range'', presented at the 7th International Workshop on Room Temperature Semiconductor X- and Gamma Ray Detectors and Associated Electronics'', Ravello, Italy, September 23-28, 1991. (To be published in Nucl. Instr. and Meth. B) V.Vylet, ``Delta Factor in Irradiation Geometry Correction'', ANS Transactions, TANSAO 64 1-754, p 470, 1991. M.C.Torres, A.J. Elwyn and V.Vylet, ``Neutron Spectral Measurements outside Shielding at an 800-GeV Proton Accelerator'', ANS Transactions, TANSAO 64 1-754, p 476, 1991. R.Yotam, J.Cerino, R.Garoutte, R.Hettel, M.Horton, J.Sebek, E.Benson, K.Crook, J.Fitch, N.Ipe, G.Nelson, and H.Smith, ``Personnel Protection and Beam Containment for the 3 GeV Injector'' in the Proceedings of the IEEE 1991 Particle Accelerator Conference, May 6 - May 9, 1991, San Francisco, California. NEWS FROM CEBAF (Robert May ) ========================================================================= The Front End Test (FET) of CEBAF's 45 MeV superconducting injector has met its basic objective of validating system design through demonstrated beam performance using production hardware and software. As the first integrated test of systems identical to those being prepared for the two linacs of the 4 GeV recirculating accelerator, the FET provides both essential design feedback and valuable experience for commissioning and operation of the full machine. CW beam has been produced at 45 MeV and 200 microamperes, meeting specifications. Emittance and momentum spread specifications have also been achieved, and the RF control module design has been fully validated, with tight phase and amplitude control attained in the presence of microphonics. Test results have shown excellent agreement with simulations. The FET has included over 9 weeks of 24-hour operation and over 800 hours of superconducting radio-frequency component operation, including thermal cycles. Testing has included recirculation of 45 MeV beam through the injector's two 20 MeV cryomodules to reach 85 MeV. Both the FET and its recirculation experiments are continuing. NEWS FROM TRIUMF (Lutz Moritz MORITZ@TRIUMFCL) ===================================================================== We are well into our spring shutdown with the major tasks well on their way to completion. Four more resonator segments are being replaced in the 500 MeV cyclotron. This work is done almost entirely remotely as the induced radiation fields in the cyclotron are greater than 5 mGy/h. All 80 resonator segments will eventually be replaced by the new stiffer design to reduce mechanical vibration. The septum magnet in the high energy pion channel has been removed in order to repair a water leak. The task of removing the magnet from the beamline is done with long-handled tools and the repair itself is carried out in a hot cell. Induced radiation fields are typically 0.3 Gy/h at 1 metre from the magnet. Once the resonator segment replacement is completed a number of tests are planned for the `alternate extraction system'. This is a system of RF booster cavities and deflectors followed by an electrostatic septum which is designed to extract a negative hydrogen ion beam from the cyclotron. The purpose of this is to be able to strip the hydrogen ions during the injection into a booster synchrotron. By using the stripping process at this stage it is possible to `paint' the phase space in the synchrotron with the beam extracted from the cyclotron. Two years ago a new cyclotron (TR-30) designed by TRIUMF and built by a local manufacturer was installed at TRIUMF for the purpose of radioisotope production. Great care was taken in designing the cyclotron and the support facility in such a manner as to minimize the dose to maintenance and support staff. After more than a year of operation we are able to compare the performance of this cyclotron to our eight year old CP-42 and find that the TR-30 produces more than twice the beam current (two simultaneous beams of 250 microamperes each) but generates less than 5% of the maintenance dose as compared to the CP-42. ANNOUNCEMENTS ======================================================================== Accelerator Section Update (Wade Patterson ) ------------------------------------------------------------------------- The Accelerator Section will be trying something new, beginning now. We intend to make E-mail our primary, and potentially only, communication medium for our Section. We do this to improve efficiency and speed, reduce the use of paper, and increase the ease of communication. In-so-far as possible the Accelerator Section will be using the IARPE Newsletter to communicate with members and other subscribers, so watch for the minutes of Section Meetings, bulletins and announcements to appear. Wade Patterson is the President of the Section Accelerator Section Meeting, IRPA (Ralph Thomas ) ------------------------------------------------------------------------- There will be an Accelerator Section Meeting at the IRPA Congress in Montreal in Room 405A, Palais des Congres on Tuesday 19 May 1992, at 5:30 pm. Members and non-members are invited to attend the meeting. Ralph Thomas is the President-Elect of the Section Accelerator Section Meeting, HPS (Goeff Stapleton ) ------------------------------------------------------------------------- There will be an Accelerator Section Meeting at the Annual HPS Meeting in Columbus, Ohio (June 21-25, 1992). The date and venue will be announced shortly. If any members of the Section wish to make suggestions for agenda items, either for the executive board meeting or the main section meeting, please contact Geoff. Goeff Stapleton is the Secretary of the Section International Conference (Wes Dunn ) ------------------------------------------------------------------------- The Twelfth International Conference on the Application of Accelerators in Research & Industry" will be held November 2-5, 1992, at the University of North Texas, Denton, Texas (approx 35 miles north of Dallas). Chairmen: Jerome L. Duggan, UofNT (817) 565-3252 BITNET:FC66@UNTVAX.BITNET I.L. Morgan, IDM Inc, Austin Fee: (before/after 10/1/92) University $170/$200 Industry/Govt $250/$275 At least 4 workshops will be held during the weekend prior to the conference at $35 per workshop and a banquet at $15 per person. There will be an Exhibit Show throughout with about 50 associated companies/vendors displaying their wares. There will be a session relating to health physics aspects which will mainly cover production accelerators. More information will be provided as soon as the abstract submission process is completed. Bulletin Board Service (Carl Schopfer ) ------------------------------------------------------------------------- Hector Mandel runs a bulletin board service that is of interest to health physicists. Available files include the recent Placement listings in the Health Physics Newsletter (before they are published!) Files can be perused or downloaded from the Check Source BBS (217) 244-6954, up to 34K bps, 8 bits, no parity, 24 hours per day. The collection of health physics files as well as the job placement ads and the list of continuing education courses are also available for anonymous FTP from romulus.ehs.uiuc.edu (128.174.74.24). QUESTIONS? QUESTIONS? QUESTIONS? ========================================================================= Neutron Yields (Tony Greenhouse ) ------------------------------------------------------------------------- We are looking for neutron yields from 0.6 to 1 GeV protons incident on uranium targets. The information is needed for LBL's proposed IsoSpin Radioactive Beam Accelerator in which a proton synchrocyclotron will be used to bombard a variety of targets to produce radioactive species. Any information will be most appreciated. Please respond via e-mail to RJDonahue@lbl.gov. ======================================================================== FEATURE ARTICLE OF THE MONTH ======================================================================== MEDICAL CYCLOTRONS by R. C. McCall ------------------------------------------------------------------------ There is an active and increasing interest in positron emission tomography (PET). This is the visualization of structures in the human body by labelling them with positron emitting isotopes and detecting the annihilation gamma rays externally. In order to achieve the desired sensitivity and still keep the radiation dose to the patient sufficiently low, it is necessary to use short lived radioisotopes. This in turn requires the radioisotope production facility to be close at hand in the hospital. The radioisotopes must also be elements that can be quickly incorporated into suitable chemical forms that the body will take up and concentrate in the desired organs. Popular PET isotopes are Carbon-11, Nitrogen-13, Fluorine-18, and Oxygen-15, with half-lives of about 20 minutes, 10 minutes, 110 minutes, and 2 minutes, respectively. Production is usually by cyclotrons wtih proton beams up to 18 MeV and deuteron beams up to 7 MeV. An early attempt to make carbon-11 at SLAC by photoproduction was hampered by the 2 mile distance to the hospital. Placing a cyclotron in a hospital poses some interesting shielding problems. Space is at a premium and it is always desireable and sometimes necessary to keep the shielding as thin as possible. On the other hand, most hospital workers are not radiation workers and the patients include children and pregnant women so that shielding goals may be as low as 100 mrem/year. One would expect that since cyclotrons of this energy have been around for many years that there would be an abundance of shielding data available in the literature. However, this is not the case. Apparently, since these were mostly research machines, the attitude was to just put in 10 or 12 feet of concrete all around and not worry about calculations. This approach is not possible in the cramped space of hospitals. Even the shielding data in NCRP Report 51 are found to be based on calculations and measured neutron spectra if you examine them carefully. One is inclined to be a little skeptical when you see that some of the transmission curves are extended over 8 or 9 decades! In general, neutron spectra from the PET isotope production reactions are not available. Some of them have spectra at lower bombarding energies published in the literature and it is possible to make reasonable estimates of what happens to the spectra as the energy is increased. The same is true for the gamma ray spectra. However, the neutron and gamma-ray dose equivalent from targets during production are of the order of 1000 and 500 rem/hour at one meter, respectively. Since the cyclotrons are expected to run during most of the 40 hour week, an attenuation factor of about 6 orders of magnitude must be obtained. This is in addition to the roughly one order of magnitude obtained by distance. Even with long computer times, Monte Carlo calculations will not give good results for such deep penetration problems. It should be noted that door designs are also more critical. Radiotherapy electron linac rooms have been built with no mazes. However, the shielding attenuation is only about three orders of magnitude compared with about 6 orders of magnitude needed for these cyclotrons. Small gaps in or around the door become much more important. Faced with such a problem, the radiation physicist designing the shield has few options. He is caught between the Scylla of a cyclotron that cannot be operated because of inadequate shielding and the Charybdis of one that cannot be built because there is no room for a massive shield. One approach is to reduce the unknown high energy neutron spectrum to a predictable one by the use of iron or lead shields. This simplifies the problem since the spectra now have an average energy of about 1 MeV with lead or 0.7 MeV with iron. One still worries about high energy tails that penetrate the metal shielding and are significant after 5 or 6 decades of concrete shielding. The use of the metal shielding also helps the gamma-ray shielding problem. Not only does it attenuate the gammma-rays efficiently but it tends to concentrate the transmitted spectrum into the minimum of the metal's absorption coefficient curve. By this technique, the calculations indicate shield thicknesses ranging around 6 feet of normal concrete. In a year or two these facilities will be coming on line and we will know if the calculations work or not. Dick McCall, the former RSO and Head of the Radiation Physics Department at SLAC, now works as a consultant out of his home. CLOSING THOUGHTS ========================================================================= ``Character is what you are in the dark.'' Dwight L. Moody, Sermons