Neutron sources

The 704 MHz SRF gun for the BNL Energy Recovery Linac (ERL) prototype uses two fundamental power couplers (FPCs) to deliver up to 1 MW of CW RF power to the half-cell cavity. To prepare the couplers for high-power RF service and process multipacting, the FPCs should be conditioned prior to installation into the gun cryomodule. A room-temperature test stand was configured for conditioning FPCs in full reflection regime with varied phase of the reflecting wave. The FPCs have been conditioned up to 250 kW in pulse mode and 125 kW in CW mode. The multipacting simulations were carried out with Track3P code developed at SLAC. The simulations matched the experimental results very well. This paper presents the FPC RF and thermal design, multipacting simulations and conditioning of the BNL gun FPCs.

Initial physical dosimetry measurements have been completed using activation spectrometry and thermoluminiscent dosimeters to characterize the BNCT irradiation facility developed at the RA-1 research reactor operated by the Argentine National Atomic Energy Commission in Buenos Aires. Some biological scoping irradiations have also been completed using a small-animal (hamster) oral mucosa tumor model. Results indicate that the RA-1 neutron source produces useful dose rates but that some improvements in the initial configuration will be needed to optimize the spectrum for thermal-neutron BNCT research applications.

A residual gas fluorescence beam profile monitor at the relativistic heavy ion collider (RHIC) has successfully recorded vertical beam sizes of Au-ion beams from 3.85 to 100 GeV/n during the 2010 beam runs. Although the fluorescence cross section of Au-ion is sufficiently large, the low residual gas in a typical vacuum chamber of <10 -9 torr produces necessary weak fluorescence photons. However, with adequate CCD exposure time, the vertical beam profiles are captured to provide an independent measurement of the RHIC beam size and emittance. This beam diagnostic technique, utilizing the Au-ion beam induced fluorescence from residual gas where hydrogen is still the dominant constituent in nearly all vacuum system, represents a step towards the realization of a truly noninvasive beam monitor for high-energy particle beams.

The need is increasing for development of high-power targets and beam dump areas for the production of intense beams of secondary particles. The severe constraints arising from a megawatt beam deposited on targets and absorbers call for nontrivial procedures to dilute the beam. This study describes the development of targets and absorbers and the advantages of using flowing liquid metal in concave channels first proposed by IFMIF to raise the liquid metal boiling point by increasing the pressure in liquid supported by a centrifugal force. Such flow with a back-wall is subject to Taylor-Couette instability. The instability can play a positive role of increasing the heat transfer from the hottest region in the target/absorber to the back-wall cooled by water. Results of theoretical analysis and numerical modeling of both targets and dump areas for the IFMIF, ILC, and RIA facilities are presented.

Communications and Power Industries (CPI) and AMAC International have jointly developed window couplers for superconducting accelerators operating at 805 MHz. Three window, couplers where delivered to Jefferson Labs in the spring of 2002. The couplers were conditioned at JLAB at room temperature and were successfully qualified as prototypes for the SNS in May 2002. The couplers reached 1 MW traveling wave at 1 ms pulse widths for 30 Hz and 2.8 MW standing wave at 0.15 ms for 60 Hz.

Most studies of dense plasma focus devices use cylindrical coaxial shapes, however, a spherical shape is investigated herein. Snow plow model and shock wave equations are coupled with the circuit equations to model the spherical plasma focus. Of interest in spherical plasma focus is to have both sheath expansion and the magnetic pressure changing rate for the rundown phase instead of the constant sheath only for the cylindrical case. The developed model is compared to published experimental results for validation and good agreement was obtained. Hydrogen and its isotopes were separately used for investigating the effect of the different molecular weights on plasma parameters. The gas pressure and discharge voltage were varied for these gases to study their effect on the plasma parameters. The study predicts a peak discharge current of 1.5MA for tritium with 0.92MA dip discharge current, and less for deuterium and hydrogen. The current drop for tritium indicates focus action. It indicates that the sheath velocity for heavy gases is lower than lighter gases. Predicted maximum temperature variation is about 11.1eV for hydrogen, 14.6eV for deuterium, 15.9eV for DT mixture and 17eV for pure tritium; which indicates higher temperature with heavier gasses.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employets, makes any warranty, express or implied. or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, m mmendation, or favoring by the United States Government or any agency thereof.

We present recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source (SNS) at Oak Ridge, and updated results for the Proton Storage Ring (PSR) at Los Alamos. In particular, a complete refined model for the secondary emission process including the so called true secondary, rediffused and backscattered electrons has been included in the simulation code.

The Low Energy Neutron Source (LENS) is an accelerator-based pulsed cold neutron facility under construction at the Indiana University Cyclotron Facility (IUCF). The idea behind LENS is to produce pulsed cold neutron beams starting with ∼MeV neutrons from (p,n) reactions in Be which are moderated to meV energies and extracted from a small solid angle for use in neutron instruments which can operate efficiently with relatively broad (∼1 msec) neutron pulse widths. Although the combination of the features and operating parameters of this source is unique at present, the neutronic design possesses several features similar to those envisioned for future neutron facilities such as long-pulsed spallation sources (LPSS) and very cold neutron (VCN) sources. We describe the underlying ideas and design details of the target/moderator/reflector system (TMR) and compare measurements of its brightness, energy spectrum, and emission time distribution under different moderator configurations with MCNP simulations. Brightness measurements using an ambient temperature water moderator agree with MCNP simulations within the 20% accuracy of the measurement. The measured neutron emission time distribution from a solid methane moderator is in agreement with simulation and the cold neutron flux is sufficient for neutron scattering studies of materials. We describe some possible modifications to the existing design which would increase the cold neutron brightness with negligible effect on the emission time distribution. 1

One outstanding property of pinch plasmas (Z-pinch, plasma focus, capillary discharge) is the generation of intensive very high energy electron and ion beams caused by high-amplitude electromagnetic fields. High-temperature dense magnetized plasmas are produced in high-current electrical discharges of various geometries by fast magnetic and shock compression. If the discharge is operated in deuterium gas, fusion reactions take place. It has been found from neutron emission characteristics that most of the fusion reactions are from the beam target and not from thermonuclear processes. Ion trajectories within and outside the plasma can be described by a generalized gyrating particle model (GPM). The results of space-, time-, and energy-resolved measurements of fusion neutrons (2.45 MeV) and protons (3 MeV), obtained from a 500-kJ plasma focus, are presented. Results are interpreted based on the GPM.

In spallation neutron sources, liquid mercury is the subject of big thermal and pressure shocks, upon adsorbing the proton beam. These changes can cause unstable bubbles in the liquid, which can damage the structural material. While there are methods to deal with the pressure shock, the local temperature shock cannot be avoided. In our paper we calculated the work of the critical cluster formation (i.e. for mercury micro-bubbles) together with the rate of their formation (nucleation rate). It is shown that the homogeneous nucleation rates are very low even after adsorbing several proton pulses, therefore the probability of temperature induced homogeneous bubble nucleation is negligible.

An intensity upgrade of Japan Proton Accelerator Research Complex (J-PARC) included the installation of a new ion source (IS) and a radio-frequency quadrupole (RFQ) which to be used at first stage of acceleration. The linac is divided into two sections on the basis of operating frequencies and three sections on the basis of family of RF cavities to be used for the acceleration of 50 mA beam of H − ions from 50 keV to 400 MeV. Low energy part of linac consists of an IS, a two-solenoid beam transport (LEBT) and the RFQ. The transition from one section to another can limit the acceptance of the linac if these are not matched properly in both longitudinal and transverse plane. Initially, we have calculated the acceptance of the RFQ at zero current in which space charge effects are not considered. In addition, a particle tracking technique is employed to study the space charge effects in LEBT of the J-PARC linac after the intensity upgrade in order to match the beam to the RFQ. Also, RFQ tank level and intervene voltage calibration factor is determined by comparing the simulation results of the beam transmission with the test measurement of tank level vs. transmission.

ADAM (Application of Detectors and Accelerators to Medicine) is a CERN spin-off company currently working on the construction and testing of the LIGHT (Linac for Image-Guided Hadron Therapy) machine. LIGHT is an innovative high-frequency linac based proton therapy system designed to accelerate protons up to 230 MeV: it consists of three different linac sections i.e. a 750 MHz Radio Frequency Quadrupole (RFQ) accelerating the beam up to 5 MeV; a 3 GHz Side Coupled Drift Tube Linac (SCDTL) up to 37.5 MeV; and a 3 GHz Coupled Cavity Linac (CCL) section up to 230 MeV. The compact and modular design is based on cutting edge technologies developed for particle colliders and adapted to the needs of hadron therapy beams. The LIGHT development machine is currently being built at CERN and this paper describes its design aspects and its different stages of installation and commissioning.

We describe the development of a large area neutron detector based on a pulse-mode ionization chamber lined with 6 Li foil in a low-cost housing of HDPE (High Density Polyethylene) that serves as the moderator. The use of inexpensive materials, technology for mass production and simple construction, which integrates the basic components of the sensor together, results in a substantial cost reduction. For a given sensor size, detection efficiency, or counting time, the proposed detector is expected to provide an order-of magnitude cost reduction compared to current neutron detection technology. This paper describes the detection concept including the optimization of the design using neutron transport calculations. It also gives experimental results on some prototype units using neutron and gamma sources. The properties affecting long term counting stability are discussed. An approach to reduce the effect of outgassing from the HDPE body is suggested. 3 He proportional counters would be the ideal detector for thermal neutrons if their cost allowed implementation on as large a scale as homeland security requires.

We present a readout system for thermal neutron detection. Redesigning neutron detector electrical fields can speed time response without an increase in gamma sensitivity. Gamma distribution affects the neutron counting area as single events rather than pileup of very low amplitude pulses. Operation at negative bias can resolve humidity issue. New shaper design could improve dead time and capacitance tolerance over what is commercially available .

We present a readout system for thermal neutron detection. Redesigning neutron detector electrical fields can speed time response without an increase in gamma sensitivity. Gamma distribution affects the neutron counting area as single events rather than pileup of very low amplitude pulses. Operation at negative bias can resolve humidity issue. New shaper design could improve dead time and capacitance tolerance over what is commercially available .

In contrast to freely rising bubbles, attached bubbles experiences different acceleration/deceleration fields  wall hydrophobicity strongly affects the bubble profile  Depending on the wall wettability and Bond numbers, the wall-bounded bubbles are influenced by different forces.  Different Bubble profile formation results in rise up with different velocities.  Bubbles with contact angles less than 90° move with a speed even higher than freely rising bubbles.

In contrast to freely rising bubbles, attached bubbles experiences different acceleration/deceleration fields  wall hydrophobicity strongly affects the bubble profile  Depending on the wall wettability and Bond numbers, the wall-bounded bubbles are influenced by different forces.  Different Bubble profile formation results in rise up with different velocities.  Bubbles with contact angles less than 90° move with a speed even higher than freely rising bubbles.

A growing community of scientists has been using neutrons in the most diverse areas of science. In order to meet the researchers demand in the areas of physics, chemistry, materials sciences, engineering, cultural heritage, biology and earth sciences, the Brazilian Multipurpose Reactor (RMB) will provide 3 thermal guides and 3 cold guides, with the installation of several instruments for materials characterization. In this study, we present a standard design requirement of two primordial instruments, namely Sabiá and Araponga. They are, respectively, cold and thermal neutron instruments and correspond to a Small-Angle Neutron Scattering (SANS) and High-Resolution Powder Neutron Diffractometer (HRPND) to be installed in the Neutron Guide Building (N02) of RMB. To provide adequate flux for both instruments, we propose here an initial investigation of the use of simple and split guides to transport neutron beams to two different instruments on the same guide. For this purpose, we use Monte Carlo simulations utilizing McStas software to check the efficiency of thermal neutron transport for different basic configuration and sources. By considering these results, it is possible to conclude that the split guide configuration is, in most cases, more efficient than cases that use transmitted neutron beams independently of source. We also verify that the employment of different coating indexes for concave and convex surfaces on curved guides is crucial, at least on simulated cases, to optimise neutron flux (intensity and divergence) and diminish facility installation cost.

The target vessel, which enclosing liquid mercury, for the pulsed spallation neutron source at the J-PARC is severely damaged by cavitation caused by proton beam-induced pressure waves in mercury. To mitigate the cavitation damage, we adopted a double-walled structure with a narrow channel for the mercury at the beam window of the target vessel. In addition, gas microbubbles are injected into the mercury to suppress the pressure waves. The narrow channel disturbs the growth of cavitation bubbles due to the pressure gradient. After finishing service operation, the front end of the target vessel was cut out, allowing us to inspect the effect of these cavitation damage mitigation technologies on the interior surface. The damage depth of the cutout specimens was quantitatively investigated by the replica method. The results showed that the erosion depth due to cavitation in the narrow channel is clearly smaller than on the wall facing mercury with injecting gas microbubbles.

The liquid mercury target system for the Japan Spallation Neutron Source (JSNS) at the Materials and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC) is designed to produce pulsed neutrons. The mercury target vessel in this system, which is made of type 316L stainless steel, is damaged by pressure wave-induced cavitation due to proton beam bombardment. Currently, cavitation damage is considered to be the dominant factor influencing the service life of the target vessel rather than radiation damage. In this study, cavitation damage to the interior surface of the target vessel was predicted on the basis of accumulated damage data from off-beam and on-beam experiments. The predicted damage was compared with the damage observed in a used target vessel. Furthermore, the effect of injecting gas microbubbles on cavitation damage was predicted through the measurement of the acoustic vibration of the target vessel. It was shown that the predicted depth of cavitation damage is reasonably coincident with the observed results. Moreover, it was confirmed that the injection of gas microbubbles had an effect on cavitation damage.

The Turkish Accelerator Center Proton Accelerator Facility (TAC PAF) is based on a 1 MW and 2-GeV proton linac that will include both normal conducting and superconducting accelerator structures. The normal conducting part of the TAC PAF will consist of an ion source, a low energy beam transport line, a radio frequency quadrupole, a medium energy beam transport line, and two drift tube linac structures in order to accelerate the beam up to 65 MeV. Acceleration from 65 MeV up to 2-GeV energy will be provided by a SC-spoke cavity and two SC-elliptical cavities. In the long term, TAC PAF will be used as a neutron source. We report the current status of the project including accelerator structures, ion source studies, and possible experimental stations.

Approaching construction phase in Lund, Sweden, the European Spallation Source (ESS) consists of a superconducting linear accelerator that delivers a 2 GeV, 5 MW proton beam to a rotating tungsten target. As a long pulse neutron source, the ESS does not require an accumulator ring, so the 2.86 ms pulses, with repetition rate of 14 Hz arrive directly from the linear accelerator with low emittance. To avoid damage to target station components, this intense beam must be actively expanded by quadrupoles that produce a centimetre size beamlet, combined with a fast rastering system that paints the beamlet into a 160 mm by 60 mm footprint. Upstream of and within the target station, a suite of devices will measure the beam’s density, halo, position, current, and time-of-arrival. Online density measurements are particularly important for machine protection, but present significant challenges. Diverse techniques will provide this measurement within the target station, based upon secondary emi...

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The Modane underground laboratory (LSM) is the deepest operating underground laboratory in Europe. It is located under the Fr� ejus peak in Savoie Alps in France, with average overburden of 4800 m w. e. (water equivalent), providing low-background environment for experiments in nuclear and particle physics, astrophysics and environmental physics. It is crucial to understand individual sources of background such as residual cosmic-ray flux of high-energy muons, muon-induced neutrons and contributions from radionuclides present in the environment. The identified dominant sources of background are radioactive contamination of construction materials of detectors and laboratory walls, radon contamination of the laboratory air, and neutrons produced in the laboratory. The largest neutron contribution has been identified from (α, n) reactions in low Z materials (10 7-10 4 n s 1 Bq 1) and from spontaneous fission of 238 U (1:1� 10 6 n s 1 Bq 1). � Contributions from radioactive contamination of construction materials of detectors and the surrounding environment (concrete, shielding, electronics, etc.). � Radon contamination of the laboratory air. � In the absence of muons, neutrons produced in spontaneous fission processes and in (α, n) reactions of uranium and thorium and their decay products. � Cosmogenic radionuclides produced by interactions of cosmic-ray particles in construction materials exposed on the earth surface (e. g., 26 Al). � Anthropogenic radionuclides present in construction materials (e. g., 60 Co, 137 Cs). Recently frequently studied problem is the production of cosmogenic

The application of quadrupoles with high or ultra-high gradient and small apertures requires a precise control over harmonic components of the field. A simple, fast, low cost measurement method on small size PMQs (Permanent Magnet Quadrupoles) is described. It is based on the same principle of the familiar "rotating coil technique", but in this case, profiting of the small dimensions of the PMQ, it consists in rotating the PMQ itself instead of the coil. In such way a gain on accuracy and measure time is obtained. It has been applied to characterize a set of commercial PMQs with a gradient around 200 T/m and an internal radius of 3.5 mm to be mounted in a SCDTL (Side Coupled Drift Tube Linac) structure for the acceleration of a proton beam from 7 to 12 MeV. This structure has been developed in the framework of the Italian TOP-IMPLART (Intensity Modulated Proton Linear Accelerator for Radiotherapy) Project.

We are developing a sophisticated system of beam loss pattern evaluation and residual radiation estimation. We have installed a number of Neutron Detectors (ND) and Ionization Chambers along the SNS LINAC. In this paper we present our implementation and simulation of the losses by inserting Faraday Cups, using Beam Stops and running Wire Scanners at different energies. The measured losses are simulated by 3-D transport codes (GEANT4, SHIELD, MCNPX). We compare two different sets of Beam Loss Monitors (BLM): Ionization Chambers (detecting X-ray and gamma radiation) and Photo-Multiplier Tubes with a neutron converter (detecting neutrons) and show that such a combination is a better way to measure beam losses than relying on detectors of only one type. We interpret the loss signal in terms of beam current lost in the SNS LINAC with accurate longitudinal loss distribution and plan to automate beam steering according to loss-monitor readings by using a Loss Pattern Database developed by simulating different loss scenarios with the transport codes.

Low-dimensional moderators were designed for the European Spallation Source (ESS), and the same concepts can be applied to compact sources. At ESS, quasi two-dimensional (2D) high-brightness moderators will serve all the instruments of the initial suite. The design of the moderators is influenced by several factors, such as the layout of the facility, the requirements for beam extraction, and the number of instruments; these constraints led to the choice of the 2D “butterfly” moderator for ESS. In an accelerator-based compact source, such moderators can be designed in an even more efficient way than for high-power sources, taking advantage of the lower heat loads and of the more compact arrangement of the target-moderator system, which gives more freedom in the optimization of the geometrical setup. Some promising design options have been explored.

The LANSCE linear accelerator at Los Alamos National Laboratory has a long history of successful beam operations at 800 kW. We have recently studied options for restoration of high-power operations including approaches for increasing the performance to multi-MW levels. In this paper we will discuss the results of this study including the present limitations of the existing accelerating structures at LANSCE, and the high-voltage and RF systems that drive them. Several options will be discussed and a preferred option will be presented that will enable the first in a new generation of scientific facilities for the materials community. The emphasis of this new facility is "Matter-Radiation Interactions in Extremes" (MaRIE) which will be used to discover and design the advanced materials needed to meet 21 st century national security and energy security challenges [1].

The liquid mercury target system for the Japan Spallation Neutron Source (JSNS) at the Materials and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC) is designed to produce pulsed neutrons. The mercury target vessel in this system, which is made of type 316L stainless steel, is damaged by pressure wave-induced cavitation due to proton beam bombardment. Currently, cavitation damage is considered to be the dominant factor influencing the service life of the target vessel rather than radiation damage. In this study, cavitation damage to the interior surface of the target vessel was predicted on the basis of accumulated damage data from off-beam and on-beam experiments. The predicted damage was compared with the damage observed in a used target vessel. Furthermore, the effect of injecting gas microbubbles on cavitation damage was predicted through the measurement of the acoustic vibration of the target vessel. It was shown that the predicted depth of cavitation damage is reasonably coincident with the observed results. Moreover, it was confirmed that the injection of gas microbubbles had an effect on cavitation damage.

h i g h l i g h t s • We created a TRIGA facility model with CATHARE2. • We calculated a source of fission products in postulated accident conditions. • We calculated the source of Ar-41 during reactor normal operation. • We modeled the transport and release of fission products and Ar-41 at reactor stack. • Steady-state experimental Ar-41 volumetric activity is compared with the calculated activity.

Los Alamos completed the R&D program for the SNS linac in September 2002 with publication of a comprehensive report on the SNS coupled-cavity linac (CCL) hot model. In this paper we summarize the results of this R&D program and its effect on the SNS linac design. We review the design of the bridge-coupled CCL, the refinement of the design through

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The spontaneous assessment of the atmospheric cosmic radiations at aircraft flight altitudes is becoming important to airlines and certification authorities. The largest number of recorded fluxes is usually for neutrons and gamma rays. However, neutrons prove to be the greatest threat to the aircraft's electronic and electrical systems. In this context, Bombardier has launched a cosmic radiation measurement campaign, where plastic scintillators sensors are used. The use of plastic scintillators is governed by their robustness and their capability to discriminate between neutrons and gamma rays. The sensor converts deposited energy levels, induced by cosmic radiations recorded into light pulses on-board flying aircraft. The MCNP 6 (Monte Carlo N Particles) software is then used with the appropriate modeling of the plastic scintillator to simulate the corresponding light pulses, which are then compared to the measured test data. All other testing parameters (i.e., altitude, longitude, latitude, and date) are taken in consideration during the simulation process. The scintillator geometrical model and the testing parameters referred to earlier are then used by the built in Function (+F6/DE/DF) in MCNP6 to compute the light energy mean number. Finally, to calculate the light pulses mean number, the following conversion rate of the scintillator was used (8600 photons/1 MeVee). A mean relative error of 20% is deduced, when comparing the number of measured light pulses with the ones simulated with the MCNP6 software. Relatively, good agreement between both results is achieved, which falls within the acceptable practical tolerance.

The optimum focusing conditions of the Hanyang University Plasma Focus (HUPF) device have been obtained by determining maximum power input to the focusing plasma while changing pressure at one fixed electrode, which leads to the maximum neutron generation. Six electrodes of different lengths have been used according to the snow-plow model to determine the conditions for the maximum neutron production of the HUPF device, namely 1:6 Â 10 8 (n/shot) with 17 cm electrode length and a 3.4 Torr pressure.

The effects of unsteady bubble dynamics on cavitating flow through a converging-diverging nozzle are investigated numerically. A continuum model that couples the Rayleigh–Plesset equation with the continuity and momentum equations is used to formulate unsteady, quasi-one-dimensional partial differential equations. Flow regimes studied include those where steady-state solutions exist, and those where steady-state solutions diverge at the so-called flashing instability. These latter flows consist of unsteady bubbly shock waves traveling downstream in the diverging section of the nozzle. An approximate analytical expression is developed to predict the critical backpressure for choked flow. The results agree with previous barotropic models for those flows where bubble dynamics are not important, but show that in many instances the neglect of bubble dynamics cannot be justified. Finally the computations show reasonable agreement with an experiment that measures the spatial variation of p...

Facilities providing bright thermal neutron beams are of primary importance for various research topics such as condensed matter experiments, neutron-imaging or medical applications. Currently these are mainly spallation sources and nuclear reactors. However, these later facilities are ageing and the political context does not favor the building of new ones. This is the case in CEA-Saclay (France), where the Orphee reactor is planned to shutdown in 2019. Therefore, another local facility, affordable by one country, able to provide high brilliance neutron beams has to be built. At CEA-Saclay, a compact accelerator driven neutron source, SONATE, is investigated in taking advantage of the IPHI accelerator able to deliver a 3 MeV proton beam with an intensity up to 100 mA. In the future, SONATE is foreseen to operate with 20 MeV protons to increase the neutron brightness. In addition to the difficulties to operate such high intensity accelerators, the other challenges regard the target-...

The standard definition for an achromat is a transport line having zero values for the spatial dispersion (R16) and the angular dispersion (RZ6). For a bunched beam with linear space charge this definition of achromaticity does not hold. The linear space charge in the presence of a bend provides coupling between (a) bunch spatial width and bunch length (R1.5) and (b) bunch angular spread and bunch length (R25). Therefore, achromaticity should bere defined as a line having zero values of the spatial dispersion (R16), the angular dispersion (R26), and matrix elements R15 & R25. These additional conditions (R15=R25=0) can be achieved, for example, with two small RF cavities at appropriate locations in the achromat, to cancel space charge effects. An example of the application of t&s technique to the Spallation Neutron Source (SNS) high energy beam transport line will be presented.

Background: Concrete activation in cyclotron vaults is a major concern associated with their decommissioning because a considerable amount of activated concrete is generated by secondary neutrons during the operation of cyclotrons. Reducing the amount of activated concrete is important because of the high cost associated with radioactive waste management. This study aims to investigate the capability of the neutron absorbing materials to reduce concrete activation. Materials and Methods: The Particle and Heavy Ion Transport code System (PHITS) code was used to simulate a cyclotron target and room. The dimensions of the room were 457 cm (length), 470 cm (width), and 320 cm (height). Gd2O3, B4C, polyethylene (PE), and borated (5 wt% nat B) PE with thicknesses of 5, 10, and 15 cm and their different combinations were selected as neutron absorbing materials. They were placed on the concrete walls to determine their effects on thermal neutrons. Thin B4C and Gd2O3 were placed between the concrete wall and additional PE shield separately to decrease the required thickness of the additional shield, and the thermal neutron flux at certain depths inside the concrete was calculated for each condition. Subsequently, the optimum combination was determined with respect to radioactive waste reduction, price, and availability, and the total reduced radioactive concrete waste was estimated. Results and Discussion: In the specific conditions considered in this study, the front wall with respect to the proton beam contained radioactive waste with a depth of up to 64 cm without any additional shield. A single layer of additional shield was inefficient because a thick shield was required. Two-layer combinations comprising 0.1-or 0.4-cm-thick B4C or Gd2O3 behind 10 cmthick PE were studied to verify whether the appropriate thickness of the additional shield could be maintained. The number of transmitted thermal neutrons reduced to 30% in case of 0.1 cmthick Gd2O3+10 cm-thick PE or 0.1 cm-thick B4C+10 cm-thick PE. Thus, the thickness of the radioactive waste in the front wall was reduced from 64 to 48 cm. Conclusion: Based on price and availability, the combination of the 10 cm-thick PE+0.1 cmthick B4C was reasonable and could effectively reduce the number of thermal neutrons. The amount of radioactive concrete waste was reduced by factor of two when considering whole concrete walls of the PET cyclotron vault.

This document is a safety analysis of a novel neutron detection technology developed by Sandia National Laboratories. This technology is comprised of devices with tiny channels containing high pressure 3 He. These devices are further integrated into large scale neutron sensors. Modeling and preliminary device testing indicates that the time required to detect the

The Front-End Systems (FES) for the Spallation Neutron Source (SNS) project comprise an rf-driven H-ion source, an electrostatic 2-lens LEBT, a 2.5 MeV RFQ, followed by a 14-quadrupole, 4-rebuncher MEBT including traveling-wave fast choppers. The ...

Transverse beam profiles in the Relativistic Heavy-Ion Collider (RHIC) will be measured with ionization profile monitors (IPM's). Each IPM collects and measures the distribution of electrons in the beamline resulting from residual gas ionization during bunch passage. The electrons are swept transversely from the beamline and collected on strip anodes oriented parallel to the beam axis. At each bunch passage the charge pulses are amplified, integrated, and digitized for display as a profile histogram. A prototype detector was tested in the injection line during the RHIC Sextant Test. This paper describes the detector and gives results from the beam tests.