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This work compares the design and practices for radiation safety among the five SR facilities: two low-energy sources (ALS and NSLS), one medium-energy source (SSRL), and two high-energy sources (APS and SPring8). The issues addressed in this comparison are (1) safety interlock systems for ring and beamlines, (2) beam loss scenarios and shielding design for storage ring, (3) beam loss scenarios and shielding design for SR beamlines, which cover synchrotron radiation and gas Bremsstrahlung issues, (4) radiation monitors for ring and beamlines, (5) safety control issues for top-up operation, and (6) operational issues. The goals of this work are to (1) provide a framework of radiation safety issues that need to, or may, be considered in the design and operation of a SR facility, and (2) develop sound policies and practices for radiation safety of SR facilities, when it is needed and practical to do so.

Nd–Fe–B permanent magnets are highly desirable for use in the insertion devices of synchrotron radiation sources due to their high remanence, or residual magnetic induction, and intrinsic coercivity. However, the radiation environment within high-energy storage rings makes essential the determination of the degree of radiation sensitivity as well as the mechanisms of radiation-induced demagnetization. Sample Nd–Fe–B permanent magnets were irradiated at the Advanced Photon Source with bending magnet X-rays up to an absorbed dose of approximately 280 Mrad (1 Mrad=10kGy). Sample magnets were also irradiated with 60Co γ-rays up to an absorbed dose of 700 Mrad at the National Institute of Standards and Technology's standard gamma irradiation facility. Changes in the residual induction were found to be within the experimental uncertainties for both the X-ray and γ-ray irradiations. Sample Nd–Fe–B permanent magnets were then irradiated at Oak Ridge National Laboratory's Californium User Facility for Neutron Science with fast neutrons up to a total fast fluence of 1.61×1014 n/cm2, and with thermal neutrons up to a total thermal fluence of 2.94×1012 n/cm2. The fast-neutron irradiation revealed changes between residual induction measurements of the sample magnets before and after irradiation of 0.6% and greater for fast-neutron fluence levels of 2×1013 n/cm2 and above. Thermal-neutron irradiation revealed changes in the residual induction measurements of the sample magnets before and after irradiation that were within the experimental uncertainties for thermal-neutron fluence levels up to 3×1012 n/cm2.

The absorbed-dose distributions for bremsstrahlung, incident on a tissue-equivalent phantom, were measured with LiF : Mg,Ti thermoluminescent dosimeters at two insertion device beamlines of the European Synchrotron Radiation Facility (ESRF). The measurements were carried out for two different electron beam energies of 4 and 6 GeV. The corresponding bremsstrahlung spectra and power were measured using a high-resolution lead glass total absorption calorimeter. The results are compared with similar measurements carried out at other facilities. The normalized bremsstrahlung absorbed dose in a cross-sectional area of 100 mm 2 , at a depth of 150 mm of the phantom, was measured as 6.1 and 3.6 kGy h −1 W −1 for the corresponding bremsstrahlung spectra of 4 and 6 GeV.

Electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the particle beam with the residual gas molecules and other components inside the storage ring. At the Advanced Photon Source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion devices comes down through the beamlines. The resulting absorbed dose distributions by this radiation in a 300 mm × 300 mm × 300 mm tissue substitute phantom were measured with LiF:Mg, Ti (TLD-700) thermoluminescent dosimeters. The average normalized absorbed dose, in a cross sectional area of 100 mm2 at a depth of 150 mm of the PMMA phantom, was measured as 3.3 × 106 mGy h−1W−1 for a 7-GeV bremsstrahlung spectrum.

High-energy electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the particle beam with the residual gas molecules and other components inside the storage ring. At synchrotron radiation facilities, where beamlines are channeled out of the storage ring, a continuous bremsstrahlung spectrum, with a maximum energy of the stored particle beam, will be present. At the advanced photon source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion device beamlines, which are a total of 15.38 m in length, can be significant. The contribution from each bremsstrahlung interaction adds up to produce a narrow mono-directional bremsstrahlung beam that comes down through the insertion device beamlines. The resulting absorbed dose distributions by this radiation in a 300 mm×300 mm×300 mm tissue substitute cube phantom were measured with LiF:Mg,Ti (TLD-700) thermoluminescent dosemeters. The normalized absorbed dose, in a cross-sectional area of 100 mm2 at a depth of 150 mm of the PMMA phantom, was measured as 3.3×106 mGy h−1W−1 for 7-GeV bremsstrahlung spectrum.

Photons of sufficiently high energies (Eγ≥5–15 MeV) can produce neutrons by means of photonuclear interactions. Bremsstrahlung from high energy electron storage rings, which have an energy range of zero to the maximum energy of the particle beam, can interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. This paper presents the results of simultaneous measurements of bremsstrahlung power and corresponding photoneutron dose equivalent rate at the insertion device beamlines of the Advanced Photon Source, using a lead-glass calorimeter and an Andersson–Braun remmeter. Targets made of Fe, Cu, W, and Pb are placed in the bremsstrahlung beam inside the first optics enclosure of the insertion device beamlines. The photoneutron dose equivalent rates, normalized to bremsstrahlung power, beam current, and storage ring pressure, are measured for the four targets. The photoneutron dose equivalent rates, normalized to the bremsstrahlung power and corrected for systematic variations, are given as 2.2±0.5 rem/h/W for Fe,3.0±0.5 rem/h/W for Cu, 3.8±0.5 rem/h/W for W, and 3.7±0.8 rem/h/W for Pb targets, at a distance of 0.8 m perpendicular from the target center.

Bremsstrahlung is produced in electron storage rings when the particle beam interacts with the storage ring components or with the residual gas molecules in the storage ring vacuum. The interaction of the particle beam with the gas molecules occurs continuously during storage ring operation. At straight sections of a storage ring, the gas bremsstrahlung contribution from each interaction adds up to produce a narrow monodirectional photon beam that travels down the beamlines. At the Advanced Photon Source (APS), where the stored electron beam energy is 7 GeV, gas bremsstrahlung generated in the straight sections of the insertion device beamlines, which is a total of 15.38 m in effective length, can be significant. This paper presents the results of the bremsstrahlung spectrum and energy measurements from the insertion device beamlines of the APS using a hermetic lead glass calorimeter. The calorimeter consists of 25 lead glass blocks, each 6.3 cm × 6.3 cm × 35 cm, stacked into a 5 × 5 array. Phototubes connected to the lead glass blocks collected the signals. The calorimeter is calibrated using the maximum energy of the observed bremsstrahlung spectrum. The total energy radiated and the bremsstrahlung spectrum were measured as a function of the storage ring beam current for both electrons and positrons of 7 GeV energy. Vacuum in the straight section was continuously monitored, and measurements to determine the nature of the residual gas inside the storage ring were performed. The measured bremsstrahlung spectra are fitted to a function that shows an approximate 1 E behavior. The gas bremsstrahlung rate from the APS undulator beamline straight path of 15.38 m is measured as 60.0 ± 2.0 GeV/s/nT/mA. Significant contribution of bremsstrahlung from sources other than the residual gas molecules is observed. The maximum bremsstrahlung energy measured in a beamline during the experiment is 369.0 ± 22.0 GeV/s/nT/mA.

This paper presents the simulation studies with CALOR89 for the Reconfigurable-Stack calorimeter (Hanging Files) test beam measurements conducted at Fermilab during the period of September 91 to January 92. The purpose of this study is to validate the CALOR89 code against the experimental data and to enhance its reliability and predictive power, especially for the multi-segmented SDC calorimeters. The results of the simulation are compared with the measured e/π ratio, the electromagnetic and hadronic energy resolutions and the longitudinal shower profiles. These comparisons show that the CALOR89 can predict reasonably well the parameters for the scintillating plate calorimeters. We have also identified certain systematic effects in modeling the experimental configurations with CALOR89.

A comparison between the experimental data known as the “hanging file” and calculated results obtained using CALOR89 on longitudinal “energy deposition” profiles (as modified for light emission) for various calorimeter configurations is presented.

Results of the simulation studies for the design of a scintillating plate calorimeter for an SSC detector are presented. These simulation studies have been carried out with the CALOR89 code. The results show that both lead and uranium can yield good compensation in practical sampling geometries. However, the significant delayed energy release in the uranium systems can lead to a serious pile up problem at high rates. In the energy range under consideration, an iron-scintillator system is not compensating at any absorber to scintillator ratio. An inhomogeneous calorimeter with 4γ of lead-scintillator in a compensating configuration followed by 4γ of iron-scintillator with moderate sampling is found to perform as well as a homogeneous lead-scintillator compensating calorimeter. In such inhomogeneous systems the hadronic signal from different segments are weighted by a scheme based on minimum ionizing d E /d X . We show that, in a properly optimised three segment, compensation and good hadronic resolution can be achieved by appropriately weighting the signal from the segments.

The CALOR code system has been recently revised by adding a high energy collision model for energies ≥ 5 GeV. This version is called as CALOR89. Calculations with this version have been carried out and compared with experimental data from four test beam scintillator plate calorimeter configurations. The agreement is good within the systematics. The limiting uncertainty in CALOR simulation at 10 GeV is the choice of collision model. We have addressed this uncertainty by appealing to the experimental data and determined that by a careful transition from the Intranuclear Cascade model to the FLUKA model this can be reduced to 1.5%. The other mostly mechanical effects such as cladding, scintillator saturation, shower integration time and shower containment can each produce systematic shifts as much as 4%. However, careful modeling of the experimental configuration should allow the systematic effects from each of these to be minimised to 1%. We find that an overall systematic uncertainty of 2.5% in the model predictions may then be achieved.

A position-sensitive photoconductive detector (PSPCD) using insulating-type CVD diamond as its substrate material has been developed at the Advanced Photon Source (APS). Several different configurations, including a quadrant pattern for a X-ray-transmitting beam position monitor (TBPM) and 1-D and 2-D arrays for PSPCD beam profilers, have been developed. Tests on different PSPCD devices with high-heat-flux undulator white X-ray beam, as well as with gamma-ray beams from /sup 60/Co sources have been done at the APS and National Institute of Standards and Technology (NIST). It was proven that the insulating-type CVD diamond can be used to make a hard X-ray and gamma-ray position-sensitive detector that acts as a solid-state ion chamber. These detectors are based on the photoconductivity principle. A total of eleven of these TBPMs have been installed on the APS front ends for commissioning use. The linear array PSPCD beam profiler has been routinely used for direct measurements of the undulator white beam profile. More tests with hard x-rays and gamma rays are planned for the CVD-diamond 2-D imaging PSPCD. Potential applications include a high-dose-rate beam profiler for fourth-generation synchrotron radiation facilities, such as free-electron lasers.

A position-sensitive detector using insulating-type CVD diamond as its substrate material has been developed at the Advanced Photon Source (APS), Argonne National Laboratory, and was tested with a 5 MeV electron beam from a CW Rhodotron/sup TM/ accelerator at the STERIS Corporation. The preliminary test result shows that the free-standing insulating-type CVD-diamond acts as a solid-state ion chamber under the 5 MeV electron beam. Potential applications of the CVD-diamond-based position-sensitive detector, e.g., as a high-dose-rate beam profiler for industrial electron accelerators and radiation technologies are discussed in this paper.

Bremsstrahlung is generated in the storage rings of the synchrotron radiation facilities by the radiative interaction of the circulating particle beam with both the residual gas molecules and storage ring components. These bremsstrahlung photons, having an energy range of zero to the maximum energy of the particle beam, interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. There are three main processes by which photoneutrons may be produced by the high energy bremsstrahlung photons: giant nuclear dipole resonance and decay (10 MeV 140 MeV). The giant resonance neutrons are emitted almost isotropically and have an average energy of about 2 MeV. High energy neutrons (E > 10 MeV) emitted from the quasi-deuteron decay and intranuclear cascade are peaked in the forward direction. At the Advanced Photon Source (APS), where bremsstrahlung energy can be as high as 7 GeV, production of photoneutrons in varying yields is possible from all of the above three processes. The bremsstrahlung produced along a typical 15.38-m straight path of the insertion device (ID) beamline of the APS has been measured and analyzed in previous studies. High-Z materials constituting the beamline components, such as collimators and beam stops, can produce photoneutrons upon interaction with these bremsstrahlung photons. The 1/E nature of the bremsstrahlung spectrum and the fact that the photoneutron production cross section is comparatively larger in the energy region 10 MeV < E{sub {gamma}} < 30 MeV, results in the giant resonance interaction being the dominant mechanism that generates photoneutrons at the APS. Such neutron flux in the vicinities of the first optics enclosures (FOEs) of ID beamlines is important, from the point of view of radiation protection of the personnel. Only a few of such neutron flux measurements were conducted at high photon energies. Monte Carlo codes and analytical formulas are used to calculate the differential photon track length in targets. Together with the known photoneutron cross sections, the neutron yields are then determined as a function of incident electron energy. Neutron fluence calculated from these yields assumes isotropic emission of neutrons from a point source target. Because neutron transport is not handled in most of these studies, possible neutron interactions inside the target are not accounted for in calculating the energy and intensity outside the target. There is also the uncertainty of photoneutron production cross section at higher energies. A simultaneous measurement of bremsstrahlung and corresponding photoneutron production will provide photoneutron dose rates as a function of bremsstrahlung energy or power. Along with our already existing bremsstrahlung spectrum measurement expertise, we conducted simultaneous photoneutron dose measurements at the APS from thick targets of Fe, Cu, W, and Pb that are placed in the bremsstrahlung beam inside the FOE of the insertion device beamlines. An Andersson-Braun (AB) remmeter that houses a BF{sub 3} detector, as well as a very sensitive pressurized {sup 3}He detector, is used for neutron dose measurements. The dose equivalent rates, normalized to bremsstrahlung power, beam current, and storage ring vacuum, are measured for various targets. This report details the experimental setup, data acquisition system, calibration procedures, analysis of the data and the results of the measurements.

This study was aimed at determining the adequacy of the storage ring bulk shielding for reducing the radiation hazard outside of secured areas, due to errant particle beam losses. The hazard class (Low, Medium or High) of an accelerator is determined by the onsite and offsite effective dose equivalent under the assumption of a maximal credible accident occurring. The credible maximal accident condition is that which produces at the weakest part of the shielding at full power the greatest amount of radiation at the subject position outside the secured area during one hour. For the hazard class to be Low, the onsite radiation level must be between 1 and 25 rem in the one hour duration of the maximal credible accident. The safety envelope defines the bounding conditions for the safe operation of a DOE accelerator facility. The measured dose rate results at each location showed wide variations, which tends to indicate that the missteered beam may not have hit at the same point for each repeat of a given loss scenario. However, all measured results were comfortably below the calculated values. It appears the use of semi-empirical calculational methods are generally quite conservative, which is desirable for perceived beammore » loss accidents at the safety envelope. With respect to the disagreement between the calculated dose rates and the measured values for the maximal credible accident, the authors suspect that the actual showering which takes place is more distributed along the beamline than the 4-m-long beam spill assumed in the calculations. Since the distribution is not known this adds further to the difficulty in correlating the measured results with the calculated values. In all controlled loss studies, it appears that the measured results were obtained for showers that may not have been fully developed.« less

High energy electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the electrons (or positrons) with the residual gas molecules inside the storage ring. The resulting radiation exits at an average emittance angle of (m{sub 0}c{sub 2}/E) radian with respect to the electron beam path, where m{sub 0}c{sup 2} is the rest mass of E the electron and E its kinetic energy. Thus, at straight sections of the storage rings, moving electrons will produce a narrow and intense monodirectional photon beam. At synchrotron radiation facilities, where beamlines are channeled out of the storage ring, a continuous gas bremsstrahlung spectrum, with a maximum energy of the electron beam, will be present. There are a number of compelling reasons that a measurement of the bremsstrahlung characteristics be conducted at the Advanced Photon Source (APS) storage ring. Although the number of residual gas molecules present in the storage ring at typical nTorr vacuum is low, because of the long straight paths of the electrons in the storage ring at APS, significant production of bremsstrahlung will be produced. This may pose a radiation hazard. It is then imperative that personnel be shielded from dose rates due to this radiation. There are not many measurements available for gas bremsstrahlung, especially for higher electron beam energies. The quantitative estimates of gas bremsstrahlung from storage rings as evaluated by Monte Carlo codes also have several uncertainties. They are in general calculated for air at atmospheric pressure, the results of which are then extrapolated to typical storage ring vacuum values (of the order of 10{sup -9} Torr). Realistically, the actual pressure profile can vary inside the narrow vacuum chamber. Also, the actual chemical composition of the residual gas inside the storage ring is generally different from that of air.

Ozone is generated in the APS experimental stations whenever the x-ray beam has a chance to interact with air. Ozone concentrations in an experimental station have to be below a certain defined limit (current OSHA regulations specify 0.08 ppm as the maximum limit) before an experimenter can reenter the hutch. This limit is said to be currently under study for a downward adjustment. One method of depleting the ozone generated in an experimental station is mitigation through either adsorption or direct destruction. In recent tests, both methods were tried using commercially available units. Test results and some analytical predictions are presented.

The particle beam, during injection into the storage ring, can be partly lost in one of the transition regions between the storage-ring vacuum chamber and the insertion-device (ID) straight section. The transition region is a copper interface between a standard aluminum vacuum chamber and an insertion-device vacuum chamber. This can be a problem, at least in the first few insertion devices where the injected beam is still unstable. It may create higher photon and neutron dose rates in the first optical enclosures of the upstream ID beamlines adjacent to this region. This report presents the results of the dose rate estimates for such an event and some recommendations for mitigation.

In this paper, the results of simulations will be given for secondary bremsstrahlung beams that are incident upon various thicknesses of Pb at several angles.

Bremsstrahlung is produced in the APS storage ring by the interaction of positrons with the residual gas molecules in the vacuum chamber of the storage ring. The bremsstrahlung production causes a serious challenge in shielding the insertion-device beamlines because the entire straight section (15 meters) is in the line of sight of the beamline. The radiation emerges in a narrow cone tangential to the beam path with the characteristic emission angle 1/{gamma}, where {gamma} is E/mc{sup 2} which is the ratio of the kinetic energy to the rest mass for the positrons. This high-energy gamma radiation has an approximate 1/E spectrum with the maximum energy extending up to the particle energy (7 GeV for the APS). Bremsstrahlung, being high-energy photons, produces an electromagnetic shower when it encounters the beamline elements. A beamline element not thick enough to fully contain an electromagnetic shower can cause considerable scatter of the high-energy bremsstrahlung radiation. The low-energy component of the bremsstrahlung can also be scattered and create high dose rates in the first-optical and white-beam enclosures. The fully developed electromagnetic shower will have a photon spectrum almost independent of the material. The electromagnetic showers in the high-Z materials can also produce photoneutrons. This notemore » reports the summary of EGS4 calculations performed on bremsstrahlung scattering from different beamline components in a typical APS insertion-device beamline. The related recommendations for shielding are also given. The shielding criterion adopted is a total dose rate of 2.5{mu}Sv/h (0.25 mrem/h) at 30 cm from the shield.« less

Two features of high-energy hadronic cascades have long been known to shielding specialists: a) in a high-energy hadronic cascade in a given material (incident E ≳ 10 GeV), the relative abundance and spectrum of each hadronic species responsible for most of the energy deposition is independent of the energy or species of the incident hadron, and b) because π0 production bleeds off more and more energy into the electromagnetic sector as the energy of the incident hadron increases, the absolute level of this low-energy hadronic activity (E ≲ 1 GeV) rises less rapidly than the incident energy, and in fact rises very nearly as a power of the incident energy. Both features are of great importance in hadron calorimetry, where it is the “universal spectrum” which makes possible the definition of an intrinsic e h , and the increasing fraction of the energy going into π0's which leads to the energy dependence of e π . We present evidence for the “universal spectrum,” and use an induction argument and simulation results to demonstrate that the low-energy activity ss Em, with 0.80 ≲ m ≲ 0.85. The hadronic activity produced by incident pions is 15–20% less than that initiated by protons.

The high energy and high luminosity of SSC cause radiation problems to detectors. Almost all the radiation in the SDC detector comes from the 20 TeV on 20 Tev pp collisions. The design luminosity corresponds to 10{sup 8} collisions per second. This luminosity is maintained for 10{sup 7} seconds (one SSC year). It is important to know the radiation fields experienced by the tracking volume, calorimeter, electronics and the phototubes. The loss of light due to the radiation damage to the scintillators can adversely affect the physics performance of the calorimeter. Studies have been carried out earlier to estimate the radiation dose in the SDC detector. In this note we use ISAJET in combination with CALOR89 to make an accurate prediction of neutron fluence at the various locations of the SDC detector. The low energy neutron fluence is important because of their large activation cross sections. In CALOR89 the low energy neutron fluence is accurately estimated by MORSE code.

This note presents the comparison of CALOR89 simulation with the ``hanging file`` test measurements conducted at Fermilab during the period of Sep 91--Jan 92. The purpose of this study is to benchmark CALOR89 code against the experimental data to enhance its reliability and predictive power. Seven hanging file configurations were simulated. The measured values of e/{pi} ratio (the ratio of electron to pion signal at the same energy), hadronic and electromagnetic resolutions were compared with the simulations. The depth profiles of the hadronic and electromagnetic showers are also compared.

CALOR89 is a system of coupled Monte Carlo particle transport computer codes which has been successfully employed for the estimation of calorimeter parameters in High Energy Physics. In the past CALOR89 has been running on various IBM machines and on CRAY X-MP at Lawrence Livermore Lab. These machines had non-unix operating systems. In this report we present a UNIX version of CALOR89, which is especially suited for the UNIX work stations. Moreover CALOR89 is also been supplemented with two new program packages which makes it more user friendly. CALPREP is a program for the preparation of the input files for CALOR89 in general geometry and ANALYZ is an analysis package to extract the final results from CALOR89 relevant to calorimeters. This report also provides two script files LCALOR and PCALOR. LCALOR runs CALOR89 sequences of programs and EGS4 for a given configuration sequentially on a single processor and PCALOR concurrently on a multiprocessor unix workstation.

As scintillating plate calorimetry is a viable option for the SDC detector, it is imperative that the phase space of passive and active materials be explored in a systematic fashion. To this end, we have examined several different configurations of passive and active materials as a function of incident energy, to see what the resolution and e/h characteristics are of each of these configurations. These studies have been carried out using the CALOR89 Monte Carlo simulation package. 3 figs., 5 tabs.

CALOR89 Simulation code has been used to estimate the hadronic and electromagnetic resolutions for the various scintillator plate calorimeter configurations. The goal of this study was to determine the optimum combination of Lead and Iron based calorimeter, which retains compensation and linearity. The configurations considered are Lead/Scintillator and Fe/Scintillator and their combinations. Ultimately, we hope to test these configurations in the hanging file beam test at Fermilab in this spring. 12 figs., 4 tabs.

This note is the preliminary report of the results of optimisation studies at ANL for the proposed scintillator plate calorimeter for SSC. In this note we have tried to optimise some of the basic parameters for the calorimeter with the available simulation tools at ANL. These simulation studies were carried out using EGS4 and GEANT 3.11 (with GHEISHA 7 implementation) on ANL CRAY XMP14 computer. The various input parameters for GEANT and EGS were optimised and validated using the available test beam data. The codes thus validated were used to calculate some of the basic parameters for the scintillator plate calorimeter for SSC with different absorber materials.

Several collaborative access teams at the Advanced Photon Source (APS) are planning to use a vertically or horizontally reflecting mirror as the first optical element in the insertion device beamlines. The scattering of the bremsstrahlung from the glancing incidence mirrors is significantly different than that from normal incidence targets. The Electron Gamma Shower program (EGS4) was used to calculate the angular distribution of the scattered secondary bremsstrahlung from copper and silicon glancing incidence mirrors. These calculations were done for an incident angle of 0.15°. Pair production, positron annihilation at rest and in flight, Moliere multiple scattering, Moller and Bhabha scattering, delta ray production, Compton scattering, the photoelectric effect, and the continuous energy loss by Bethe‐Bloch formalism were the processes simulated in this calculation. The dose at one meter away from the mirror, due to the scattered secondary bremsstrahlung, was calculated from the energy deposited in the ...

To evaluate the feasibility of designing an economic beamline transport system for insertion device beamlines at the Advanced Photon Source, two sample cases have been designed and analyzed, one for an undulator source and the other for a wiggler source. The results show that it is possible to build a 70‐meter‐long beamline transport system for an undulator source with less than four lead/tungsten‐alloy bremsstrahlung collimators. Six or fewer collimators are needed to construct a 70‐meter‐long white‐beam transport system for a wiggler source. To prevent damage from any missteered powerful white beam, a water‐cooled fixed mask is placed in front of each collimator. Ray tracing for both bremsstrahlung and synchrotron radiation have been conducted for the sample transports. Modular mask/collimator assembly designs and ray‐tracing results are presented.

The electromagnetic shower propagation through a thin layer uranium-scintillator sampling calorimeter has been studied by EGS4. The sensitivity of the calculated sampling fraction and the resolution on the various input parameters of the EGS code has been estimated. The EGS input parameters have been optimized for a thin layer sampling calorimeter geometry. The validity of the parameter optimization has been tested against the experimental results. It has been found that with the optimized input parameters the EGS4 results are in good agreement with the experiment of the ZEUS collaboration conducted at CERN.

Beryllium experiences (n, 2n) multiplication reaction for neutrons having energy above the threshold of ≈ 1.8 MeV. In the case of beryllium-reflected/moderated reactor assemblies these (n, 2n) neutrons contribute additional reactivity. This paper evaluates the reactivity contribution due to (n, 2n) reactions in the Be and BeO reflector of reflected 233 U uranyl nitrate solution systems in spherical geometry in the light of the latest 9 Be cross-section data. The results shows that the (n, 2n) reactions in a given thickness of reflector are directly proportional to the core leakage and thus very much a function of core radius. In the core radius range of 4–15 cm the reactivity bonus due to (n, 2n) reactions in a 30-cm thick Be reflector varies from 6.2 to 3.0%, which corresponds to a critical mass saving of ≈18–9%. The corresponding reactivity contributions for BeO reflected systems are ≈25% lower.