The photoneutron yield predictions by PICA and comparison with the measurements

The photoneutron yields at higher photon energies have become very important since the advent of high energy electron accelerators. Bremsstrahlung is produced when the particle beam interacts with the storage-ring components or residual-gas molecules in the storage-ring vacuum. Bremsstrahlung thus produced interacts with the high-Z materials in the beamline like the beam dumps and collimators to produce photoneutrons. There are three modes of neutron production by bremsstrahlung. At low energies ({>=}525 MeV), photons are absorbed by the dipole interaction and the compound nucleus thus formed decays emitting protons and neutrons and other heavier particles. At higher energies ({>=}25 MeV), photon interacts with the nucleus through absorption on a quasi-deuteron, which subsequently decays producing a neutron and proton pair which can interact with the rest of the nucleus. At still higher energies the photopion production becomes possible and competes with the quasi-deuteron process. In this paper we have calculated the photoneutron yield from a thick copper target using the photonuclear interaction code PICA. Using this as the neutron source, we have calculated the dose rates through heavy concrete and compared it with the measurements made at the Advanced Photon Source at Argonne National Lab

Measurement of gas bremsstrahlung from the insertion device beamlines of the advanced photon source

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

An Experimental Study of Radiation-Induced Demagnetization of Insertion Device Permanent Magnets

High brilliance in the 3GeV new light source NSLS II is obtained from the high magnetic fields in insertion devices (ID). The beam lifetime is limited to 3h by single Coulomb scattering in the Bunch (Touschek effect). This effect occurs everywhere around the circumference and there is unavoidable beam loss in the adjacent low aperture insertion devices. This raises the issue of degradation and damage of the permanent magnetic material by irradiation with high energy electrons and corresponding shower particles. It is expected that IDs, especially those in-vacuum, would experience changes resulting from exposure to gamma rays, x-rays, electrons and neutrons. By expanding an on-going material radiation damage study at BNL the demagnetization effect of irradiation consisting primarily of neutrons, gamma rays and electrons on a set of NdFeB magnets is studied. Integrated doses ranging from several Mrad to a few Grad were achieved at the BNL Isotope Facility with a 112 MeV, 90 {micro}A proton beam. Detailed information on dose distributions as well as on particle energy spectra on the NdFeB magnets was obtained in realistic simulations with the MARS15 Monte-Carlo code. This paper summarizes the results of this study

The effectiveness of high molecular weight hyaluronic acid for knee osteoarthritis in patients in the working age: a randomised controlled trial

Background: High molecular weight (HMW) hyaluronic acid (HA) is a treatment option for knee osteoarthritis (OA). The efficacy of HMW-HA in knee OA is investigated extensively, but the effectiveness in patients in the working age is unknown. Nevertheless, the number knee OA patients in the working age is increasing. Surgical treatment options are less eligible in these patients and productivity losses are high. In this study the effectiveness of intraarticular HMW-HA added to regular non-surgical usual care in everyday clinical practice (UC) compared to UC over 52 weeks in symptomatic knee OA patients in the working age was investigated. Methods: In this open labelled randomized controlled trial, subjects aged between 18 and 65 years with symptomatic knee OA (Kellgren and Lawrence I-III) were enrolled and randomized to UC + 3 weekly injections with HMW-HA (intervention) or UC only (control). The primary outcome was the between group difference in responders to therapy according to OMERACT-OARSI criteria after 52 weeks. These criteria include the domains pain, knee related function and patient’s global assessment (PGA). Function was evaluated with the KOOS questionnaire. Pain was assessed with the Numeric Rating Scale. Secondary outcome comprised the between group difference on the individual responder domains, as analysed with a random effects model. Odds Ratios (OR) were calculated by logistic regression analysis. Sensitivity analyses were performed. Results: In total, 156 subjects were included (intervention group 77, control group 79). Subjects in the intervention group (HMW-HA + UC) were more often responder compared to the controls (UC). Depending on whether pain during rest or pain during activity was included in the responder domains, 57.1% versus 34.2% (p = 0.006) and 54.5% versus 34.2% (p = 0.015) was responder to therapy respectively. The results of the secondary

Dose Measurements of Bremsstrahlung-Produced Neutrons at the Advanced Photon Source

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

Shielding Calculations for NSLS-II Beamlines.

Brookhaven National Laboratory is in the process of designing a new Electron Synchrotron for scientific research using synchrotron radiation. This facility, called the 'National Synchrotron Light Source II' (NSLS-II), will provide x-ray radiation of ultra-high brightness and exceptional spatial and energy resolution. It will also provide advanced insertion devices, optics, detectors, and robotics, and a suite of scientific instruments designed to maximize the scientific output of the facility. The project scope includes the design, construction, installation, and commissioning of the following accelerators: a 200 MeV linac, a booster accelerator operating from 200 MeV to 3.0 GeV, the storage ring which stores 500 mA current of electrons at an energy of 3.0 GeV and 56 beamlines for experiments. It is planned to operate the facility primarily in a top-off mode, thereby maintaining the maximum variation in stored beam current to &lt; 1%. Because of the very demanding requirements for beam emittance and synchrotron radiation brilliance, the beam life-time is expected to be quite low, on the order of 2 hours. Each of the 56 beamlines will be unique in terms of the source properties and configuration. The shielding designs for five representative beamlines are discussed in this paper

Dose rate estimates in the first optical enclosure due to particle beam loss in the insertion device transition region during injection

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

Estimation of hadronic and EM resolution for scintillator plate calorimeter configurations

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

SHIELDING REQUIREMENTS FOR NSLS-II.

Brookhaven National Laboratory is in the process of designing a new Electron Synchrotron for scientific research using synchrotron radiation. This facility, called the 'National Synchrotron Light Source II' (NSLS-II), will provide x-ray radiation of ultra-high brightness and exceptional spatial and energy resolution. It will also provide advanced insertion devices, optics, detectors, and robotics, and a suite of scientific instruments designed to maximize the scientific output of the facility. The project scope includes the design, construction, installation, and commissioning of the following accelerators: a 200 MeV linac, a booster accelerator operating from 200 MeV to 3.0 GeV, and the storage ring which stores a maximum of 500 mA current of electrons at an energy of 3.0 GeV. It is planned to operate the facility primarily in a top-off mode, thereby maintaining the maximum variation in stored beam current to &lt; 1%. Because of the very demanding requirements for beam emittance and synchrotron radiation brilliance, the beam life-time is expected to be low, on the order of 2-3 hours. Analysis of the bulk shielding for operating this facility and the input parameters used for this analysis are discussed in this paper. The characteristics of each of the accelerators and their operating modes are summarized with the input assumptions for the bulk shielding analysis