INTERNATIONAL ACCELERATOR RADIOLOGICAL PROTECTION E-MAIL (IARPE) NEWSLETTER "The Official Publication of the Accelerator Section of the Health Physics Society" (with Contributions from International Correspondents) ====================================================================== Nov./Dec. 1996 Circulation: 208 Vol.5, #6 ====================================================================== OFFICERS OF THE ACCELERATOR SECTION President: Lutz Moritz, TRIUMF President-Elect: Vashek Vylet, SLAC Past President: Bob May, TJNAF Secretary: Scott Walker, LANL Treasurer: Carter Ficklen, TJNAF Newsletter Editor: James C. Liu, SLAC Directors: Wes M. Dunn (1999) Steve Musolino (1999), BNL Jeff Leavey (1998), IBM Tracy Tipping (1998), KSU Don Cossairt (1997), FNAL Lorraine Day (1997), LSU ====================================================================== CONTENTS From the Editor Feature Article: High Mono-Energetic Neutron Calibration Facilities and Associated R & D Programs In Japan News from Correspondents: DESY, FNAL, LANL, TJNAF How to Subscribe or Update Subscription Closing Thoughts ====================================================================== From the Editor James C. Liu ====================================================================== This is a holiday season issue. Many colleagues probably are still on their vacations or just got back to work. I hope you all had a great Christmas and New Year. In this short issue, we are glad to have Professor T. Nakamura to give us the feature article introducing the three high mono-energetic neutron (> 20 MeV) calibration facilities and the associated R & D programs in Japan. In addition, we also have four news contributions from DESY, FNAL, LANL and TJNAF. The R&D news of LANL is enlightening and encouraging, particularly during this time that budget and man-power at most facilities are limited. The WEB-version of the current issue can be visited at "http://www.slac.stanford.edu/~james/iarpe.html". Thanks to A. Fasso, we have added a few good related-web sites. Please give it a try. Wish you have a bright 1997. ====================================================================== FEATURE ARTICLE Takashi Nakamura ==================================================================== High Mono-Energetic Neutron Calibration Facilities and Associated R & D Programs In Japan T. Nakamura, Professor Cyclotron and Radioisotope Center Tohoku University, Sendai 980-77, Japan Quasi-monoenergetic high energy neutron fields, produced by 7Li(p,n) reaction, have been developed at three cyclotron facilities in Japan; Cyclotron and Radioisotope Center of Tohoku University, Aoba, Aramaki, Sendai, Miyagi (CYRIC), Takasaki Research Establishment of Japan Atomic Energy Research Institute, Watanuki-cho, Takasaki, Gunma (TIARA), and Institute of Physical and Chemical Research, Hirosawa, Wako, Saitama (RIKEN). These radiation fields are useful for studies related to high-energy (> 20 MeV) neutrons, e.g., dosimetry, instrument response, shielding study, etc. This article describes the set-up and beam quality of the neutron fields. Current studies in these fields are also introduced. 1) CYRIC Neutron Field The CYRIC neutron field was set up in the 45-m-long neutron TOF (time-of-flight) room. The 25 and 35 MeV proton beams were transported to the scattering chamber through a beam swinger system in the target room to hit a 2-mm-thick natural Li target with about 2 MeV loss of incident proton energy. The proton beam was inclined at 10 degrees to the horizontal line with a beam swinger in order to shield spurious neutrons produced from the Faraday cup. The neutrons produced at 10 degrees were extracted to the TOF room through the double collimators. The first collimator consists of 1-m-thick concrete with a 20 cm x 8 cm aperture. The second collimator, which is situated in a 2.83-m-thick concrete wall with a 100 cm x 50 cm aperture, consists of 30-cm-thick iron and 30-cm-thick polyethylene with a 30 cm x 20 cm aperture. For measurement of the absolute fluence of neutrons in the high energy peak and relative spectral neutron fluence, three methods were used; a proton recoil counter telescope (PRT), an activation method of Li target, and the TOF method using an organic liquid scintillator. The PRT consists of Si-SSD dE counter and NaI(Tl) E counter coupled with a large annular type polyethylene radiator. The absolute neutron fluence of the mono-energetic peak region is also given by the activation technique of the Li target using the 7Be activity from the 7Li(p,n)7Be reaction. Two monoenergetic peaks at 22.2 and 32.9 MeV (with a 1.9 and 1.8 MeV FWHM, respectively) can be obtained by 25 and 35 MeV proton bombardment, respectively. The spectra have low energy continuum(s), coming from the higher excited states of 7Be. The neutron fluence during the experiment is monitored simultaneously with the 238U fission chamber at a fixed location close to the target. The 22.2 and 32.9 MeV peak neutron fluences are 1.2E3 and 1.8E3 n cm-2 microC-1 at the collimator exit about 8.6 m from the target. The neutron beam size is 20 cm x 30 cm, the fluence fraction of the low energy continuum is about 50% of the total, and the highest proton beam intensity is about 1 microA. In this neutron field, calibration experiments for various neutron detector responses have been done. 2) TIARA Neutron Field The TIARA neutron field has been established for the neutron shielding and cross section experiments. The 3.6 to 6.6 mm thick 99.9%-enriched 7Li targets, positioned in a target chamber in the cyclotron room, were bombarded by the proton beams of 45, 50, 55, 60, 65, 70, 80 and 90 MeV at 0 deg. The protons that penetrated the target were bent down toward the beam dump by the clearing magnet and their integrated charges were measured with the current integrator through a Faraday cup. The neutrons produced at 0 deg were extracted through a 10.9-cm-diam collimator penetrating a 220-cm-thick concrete wall between the cyclotron and the experimental rooms. An empty space of 120 x 120 x 120 cm, with 340-cm-thick concrete walls, is equipped for shielding experiment. The absolute fluences of source neutrons in the monoenergetic peak per proton beam charge were determined with the same PRT as used in the CYRIC field. The neutron fluence during the experiment was monitored simultaneously with the 238U and 232Th fission chambers fixed close to the target. The energy spectra were measured with the PRT and the TOF method using the BC501A organic liquid scintillator. The TOF spectra and the PRT spectra show good agreement at both the peak region and the continuum region. The peak neutron fluences are 17000-40000 n cm-2 microC-1 at the collimator exit 4 m behind the target for 45 to 90 MeV proton beams. The highest proton beam intensity is about 3 to 5 microA, the neutron beam size is 10.9 cm diam, and the fluence fraction of the low energy continuum is about 50% of the total. In this neutron field, the following studies have been done and are now in progress and planning under the Universities and JAERI collaborative research project: 1) neutron activation cross section measurement, 2) neutron spectral and dose distributions in and transmitted through material, 3) neutron leakage through labyrinth, 4) thick target neutron yield measurement with light heavy ions, 5) charged particle production cross section measurements, such as the (n,p) and (n,d) reactions, 6) calibration and response measurements of various neutron detectors, 7) neutron scattering cross section measurement. 3) RIKEN Neutron Field The RIKEN neutron field has been established at the E4 experimental room of the separate sector ring cyclotron. Proton beams with energies of 80, 90, 100, 110, 120, 135, 150 and 210 MeV were incident on a 10 mm thick 99.8% enriched 7Li target in the target chamber through the beam swinger. Protons passed through the target were cleared out by the magnet and absorbed in the spectrograph coupled to the beam swinger system to measure the proton beam current. Neutrons produced at 0 deg were extracted through the vacuum window of 3-cm thick acrylic and transported through the iron-concrete collimator of 22 cm by 22 cm aperture and 120 cm length. The neutron spectra were measured with the TOF method using BC501A, and the absolute neutron fluence with the Li activation method using the 7Be activity from the 7Li(p,n)7Be reaction. The peak neutron fluences at the collimator exit behind 8.37 m from the target are about 13000 n cm-2 microC-1 for 80 to 210 MeV proton beams. The highest proton beam intensity is about 100 nA, the neutron beam size is 22 cm by 22 cm, and the fluence fraction of the low energy continuum is about 50% of the total. In this neutron field, the following studies have been done and are now in progress: 1) neutron activation and spallation cross section measurements, 2) thin target neutron yield measurement with light heavy ions, 3) calibration and response measurements of various neutron detectors. A neutron shielding experiment is also planned in the near future. The Japanese research groups participated in the above-mentioned studies include: 1) Prof. Takashi Nakamura's group, Cyclotron and Radioisotope Center of Tohoku University, 2) Prof. Mamoru Baba's group, Department of Nuclear Engineering of Tohoku University, 3) Prof. Tokushi Shibata's group, Institute for Nuclear Study of University of Tokyo, 4) Prof. Kazuo Shin's group, Department of Nuclear Engineering of Kyoto University, 5) Prof. Yukinobu Watanabe's group, Department of Nuclear Engineering of Kyuushuu University, 6) Prof. Hideo Hirayama's group, National Laboratory for High Energy Physics (KEK), 7) Dr. Noriyoshi Nakanishi's Group, Institute of Physical and Chemical Research, 8) Dr. Hideshi Yasuda's Group, Tokai Laboratory, Japan Atomic Energy Research Institute (JAERI), 9) Mr. Susumu Tanaka's group, Takasaki Laboratory, Japan Atomic Energy Research Institute (JAERI), 10) Dr. Kazunobu Fujitaka's group, National Institute of Radiological Sciences. References 1) M.Takada, T.Nakamura, M.Baba, T.Iwasaki, T.Kiyosumi, "Characterization of 22 and 33 MeV quasi-monoenergetic neutron fields for detector calibration at CYRIC" Nucl. Instrum. Methods, A372, 253-261 (1996). 2) N.Nakao et al., "Transmission through shields of quasi-monoenergetic neutrons generated by 43- and 68-MeV protons", Nucl. Sci. Eng., 124(2), 228-242 (1996). 3) T. Nakamura et al., "Study on the behavior and transport of high energy particles through matter", Research Report for the Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture in Japan, Cyclotron and Radioisotope Center, Tohoku University, 1996, in Japanese. ====================================================================== NEWS FROM CORRESPONDENTS ====================================================================== News from DESY Herbert Dinter The running period of HERA during 1996 has come to an end in these days. The luminosity of 15/pb promised to the user at the beginning of the run could be realized - actually 17/pb were reached. The second half of the period was especially successful and therefore it was decided only to interrupt the machine operation for 4 weeks instead of having the planned shut-down of 4 months. Only the absolutely necessary maintenance works and the annual checks of the safety systems are foreseen in these weeks and the start of the running period 1997 for HERA is scheduled for the 1st of February. All the activities planned for the shut-down are postponed now to a large interruption of 6 months beginning probably in September 1997. This long interval is necessary for the further installation of the experiment HERA-B which is to go into operation in 1997. In the last months the Radiation Protection Group was the subject of a lot of personnel changes. Klaus Tesch, the head of the group, retired by the end of October and Herbert Dinter was nominated as his successor. A new second physicist, Albrecht Leuschner, was employed. He got his physical education in the former East Germany where he was involved in Radiation Protection for a long time. In the last few years he was a member of the University Zurich and worked at the PSI in Switzerland. In addition, two technicians retired and were replaced by one. So, all together the mean age of the group decreased but the workload per person increased. Presently, the Radiation Protection Group comprises 6 persons (2 physicists, 2 engineers, 2 technicians) and takes care of 9 accelerators, approximately 1200 DESY staff members and 1000 guests per month. In summer 1996 we had the pleasure to be host of Prof. Shin from the University of Kyoto, Japan. During his stay of 2 months he applied FLUKA to study shielding parameters of concrete for different particle types in the very forward direction for high energy proton beams. We enjoyed his engagement and we derived a lot of benefit from his experience. This was probably the last project we carried out with FLUKA92 still running on an IBM machine under the operating system MVS. In the near future the operation of this machine is terminated and all programs running so well since years have to be transported to the UNIX world. Fortunately we can continue performing calculations with FLUKA. We are very grateful to Alberto Fasso that he spent a lot of his time on introducing Version 96 on a DESY UNIX machine. One of our next projects will be to use FLUKA for calculations with high energy electron beams in order to be prepared for questions which will arise in connection with the discussions of the construction of a future Linear Collider. ---------------------------------------------------------------------- News from FNAL Don Cossairt The Fixed Target physics run using the Tevatron accelerator continues to develop. A great majority of the startup problems have been, or are being solved. The startup was expected to be slow due to the fact that this part of Fermilab's program has not been run for nearly four years. The special radiation measurements being conducted by the radiation safety personnel are continuing. This involves the measurement of the composition and total activity released by our various sources of airborne radioactivity. It also includes measurements of muon and neutron radiation fields using our special four wheel drive vehicle and the equipment installed within it. These measurements are generally quite tedious as it seems that there is some corollary of Murphy's Law, routinely verified, that states that if the vehicle is set up and moved into an accelerator-produced radiation field, the beam will go off. Persistence, however, eventually pays off and the measurements are, one-by-one, being accomplished. We are also now involved in supporting some of the special needs of the physics experiments for which the radiation protection staff possess special expertise and tools. These include neutron spectra measurements designed to gain a better understanding of experiment backgrounds. This is being done specifically with respect to a neutrino experiment where emulsions are being exposed. Likewise, special use TLDs are now being employed to help the experimenters keep an eye on potential radiation backgrounds that can actually cause damage or deterioration of their equipment. This is especially important for some types of solid state detectors and for plastic scintillators. Radiation damage to silicon microstrip technology is turning out to be a major concern of the physics community which we serve. --------------------------------------------------------------------- News from LANL L. Waters The mission of the APT (Accelerator Production of Tritium) project is to provide a dedicated US facility for the production of tritium in quantities of at least 2 kg/year, upgradable to 3 kg/year. DOE is following a dual track selection process, one emphasizing accelerator, the other reactor technology. The final decision between the two will be made late 1988. Meanwhile APT is engaged in an aggressive Engineering Design and Demonstration program for the accelerator, Target/Blanket, tritium extraction facility, and plant design. Many activities in the Target/Blanket area are of interest to the IARPE community, and APT welcomes the opportunity to give you an update of our progress. The current APT 2 kg baseline design is a 1300 MeV proton conventional accelerator running at 100 mAmp, upgradable to 134 mAmp for the 3kg option. A superconducting option (1300 MeV at 100 mAmp upgradable to 1700 MeV at 100 mAmp) is being investigated. The protons hit a split tungsten spallation target, producing neutrons which are multiplied and thermalized in a surrounding water cooled lead blanket. Tritium is produced by the He3(n,p) reaction, with the helium contained in many aluminum tubes throughout the blanket. The Target/Blanket ED&D activities focus on three main areas: Materials Performance, Verification of neutron/proton and tritium/proton ratios, and Neutronics Code and Data Development. Following I give an update on some of these activities. APT has a major materials irradiation program going at the LANSCE accelerator, just before the beamstop. We have over 5000 samples in the beam, including standard mechanical properties test samples, beam window material, tungsten target rods, and sample lead blanket modules. To date 2E+21 p/cm2 at the peak of the gaussian 1 mAmp 800 MeV beam has been accumulated after 2 months of running. We plan 5 more month's irradiation. There are two separate water corrosion studies being done, one in the LANSCE beam with the materials irradiation, and others done with electrons and protons at other facilities. The second provides online radiolysis analysis of water products using Raman and absorption spectroscopy. Our goal is to provide constant water corrosion mitigation during plant operation. Three other programs are underway to look at protium (H-1) and tritium implantation in aluminum. They involve studies in the materials irradiation setup, separate studies using a deuterium accelerator, and others using reactor irradiations. A number of benchmarking activities for APT have been completed or are underway primarily at the LANSCE and Saturne accelerator facilities, which measure our ability to predict the number of neutrons/proton and tritons/proton in various assemblies. We have completed neutron leakage measurements on tungsten, lead and iron targets in a variety of configurations using MnSO4 water bath at Saturne. These tests are simple configurations and are very effective code benchmarks. Measurements were taken at 400, 800, 1200, 1600 and 2000 MeV. We are also analyzing a smaller experiment done with 800 MeV protons at LANSCE in 1995. This concentrates on neutron fluence along the beam axis in a split tungsten configuration, and is a good complement to the Saturne work, which measures leakage outside of the target. These activities are largely in preparation for a full scale Target/Blanket prototype demonstration to take place at LANSCE in 1998. As a preliminary activity, we are building two non-linear magnets, which expand the beam to the 16cm x 160cm footprint needed for the target. These magnets will be tested starting March of 1997. In the theoretical department, the LAHET and MCNP Monte Carlo simulation codes are being completely merged, and last month saw the first 800 MeV proton tracked by MCNP. The merger will produce a tool with the full MCNP geometry and variance reduction capabilities for all particles at all energies. Collaborators are also investigating new optimization techniques for more effective simulation of high energy showers. LAHET physics routines, especially intranuclear cascade, pre-equilibrium and small angle processes are also being improved. In the future we will also begin the development of a high energy deterministic simulation code to aid in shielding design. New neutron as well as proton data libraries are being evaluated and processed for use in the merged code. To date we have completed all isotopes of W, Fe, and Pb, as well as C12 and O16, 20-150 MeV for neutrons and 1-150 MeV for protons. At this time, we intended to rely on improved LAHET physics models above these energies, instead of a completely table driven approach for all energies. There are too many unknowns in the physics above the pion threshold to do this now. Below 20 MeV we will rely on existing ENDF evaluations, however some of these will probably be revisited in the future. The new evaluations represent a major advance in that they contain angle-energy correlated emission spectra of light (A<4) ejectiles, and angle-integrated emission spectra for heavier recoils. In support of the data library and optical model work, a new set of neutron total cross section measurements has been completed at the LANSCE WNR continuous energy white neutron source facility. This is a follow on to the work done by Findlay, et al., (Phys Rev C, vol 47, #1, Jan 1993), and uses the same apparatus, and a large number of the original experimenters. Target measurements completed to date include: 6LiH, 7LiH, 10B, 11B, B, 13C, LiF, teflon, P, S, KF, Ti, V, Cr, Mn, Fe, Co, Ni, Mo, In, W, Au, Hg, Pb, Th, and 238U. Natural C was measured several times over the course of the run as a control. Energy range is 5-500 MeV, and may be expanded to 4-600 MeV at the completion of analysis. For most samples 1% statistical accuracy in 1% energy bins was achieved, and for thin samples the addition of a new 2 inch scintillator gave 2% accuracy in 1% bins. A second set of runs will be taken in the next WNR run cycle, at which time we will measure 4 separated isotopes of tungsten and 2 of iron, as well as deuterium. APT is also planning to expand the existing data base of neutron reaction cross sections in this same energy range during the next WNR run cycle with another experiment. This proposal is under development now. Such data, along with the total cross sections described above is needed for the APT Optical Model development project, which will provide potentials for use directly in our neutronics codes, and in nuclear data development. We are also looking in great detail at the activation cross sections of lutetium in the new LANSCE WNR GEANIE detector. Lutetium has a number of long-lived isotopes with well defined energy thresholds, however, little data is available about neutron cross sections greater than 20 MeV. By extending this data base we hope to understand the use of lutetium in high energy environments to measure neutron energy spectra. The CINDER90 code is the APT standard for activation calculations. It relies on extensive libraries of neutron activation and nuclear decay data. A program is underway to compare the latest European Activation File (EAF) library with experimental data contained in the Brookhaven CSISRS database. Discrepancies are being addressed in an ongoing effort. The CINDER90 code itself is undergoing a validation process prior to formal release. In summary, APT has an active Target/Blanket ED&D program with many collaborators, the results of which will benefit not only ourselves, but the community at large. APT is a weapons program, however the results of our ED&D activities will be made freely available to the community. Please do not hesitate to contact us with questions, and take a look at our Web page: http://strider.lansce.lanl.gov/apt/ ---------------------------------------------------------------------- News from TJNAF Bob May Jefferson Lab Program Advisory Committee to Meet in February With experimentation underway in Hall C and imminent in Halls A and B at Jefferson Lab, the eleventh meeting of the Program Advisory Committee is planned for February 3-5, 1997. As of early November 1996, five experiments have been completed in Hall C, and one more is underway for 1996. Seventy-five additional experiments are approved and in preparation, and sixteen more are conditionally approved. PAC11 will consider new proposals, updates to approved, conditionally approved, or deferred experiments, and letters of intent concerning prospective new lines of research. Deadline for all submissions is December 18, 1996. For further information please consult http://www.jlab.org/general/visit/PACpage/PACpage.html or contact the Jefferson Lab User Liaison Office by phone at (757) 269-7586, by fax at (757) 269-7003, or by e-mail at users@jlab.org. ====================================================================== HOW TO SUBSCRIBE / UPDATE YOUR E-MAIL ADDRESS ====================================================================== To add yourself to the mailing list for the IARPE Newsletter, send an e-mail message to: listserv@slac.stanford.edu The body of your message should contain the following command: subscribe iarpe-l Please don't forget to update your e-mail address if you move, change jobs or just change your computing environment. The update consists in canceling the old by 'unsubscribe' and submitting a new subscription, as illustrated below: unsubscribe iarpe-l your_old_email_address subscribe iarpe-l end If the body of your message, as in this example, contains more than a single line/command, it is good practice to finish with the 'end' command, especially if your mailer adds a signature. If you experience problems with subscribing/updating, please send me an e-mail to james@slac.stanford.edu and I will do it for you. ====================================================================== CLOSING THOUGHTS It is the province of knowledge to speak and it is the privilege of wisdom to listen. --- Oliver Wendell Holmes Executive ability is deciding quickly and getting someone else to do the work. -- John G. Pollard