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Real‐Time Dosimetry for Radiobiology Experiments Using 25 MeV LINAC

Mohammed A. Mestari, Douglas P. Wells, Linda C. DeVeaux, Alan Hunt, and Syed F. Naeem

AIP Conf. Proc. 1099, pp. 3-6; doi:http://dx.doi.org/10.1063/1.3120062 (4 pages)

Online Publication Date: 31 March 2009

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The next generation of radiobiology research requires increasingly more complex radiation sources to address questions ranging from the effects of space‐based radiation to the influence of dose rate on biological systems. The Idaho Accelerator Center (IAC) has developed a radiobiology research facility to address some of these questions. The irradiation challenge is to deliver stable and reproducible conditions of high dose rate with well‐controlled beam uniformity, dose, and dose rate under controlled temperature. In this work, we used a 25 MeV modified medical grade linear accelerator (LINAC) to obtain a high and adjustable electron dose rate. To overcome electron beam drift we used a collimator that both assisted the LINAC operator to steer the beam and ensured that regardless of beam drift, only the fixed collimated beam would irradiate the specimens. In addition, we utilized a beam flattener to keep the beam variation as low as 3% at 2.5 cm from the beam’s center, and 1% variation between the simultaneously irradiated sample tubes. We also demonstrated that a segmented Faraday “cup” (FC) array provides a useful real‐time beam scanning and monitoring system, and is promising for implementing real‐time dosimetry and control.

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87.53.Bn	Dosimetry/exposure assessment
29.20.Ej	Linear accelerators
87.50.cf	Biophysical mechanisms of interaction
87.56.nk	Collimators

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Charge Breeding Application of EBIS∕T Devices

Oliver Kester

AIP Conf. Proc. 1099, pp. 7-12; doi:http://dx.doi.org/10.1063/1.3120160 (6 pages)

Online Publication Date: 31 March 2009

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The demand of highly charged ions of isotopes from all mass regions of the nuclear chart for low energy experiment or for the post acceleration has driven the development of different charge breeding methods. Charge state breeder employ high charge state ion sources like the Electron Beam Ion Source∕Trap (EBIS∕T) and the Electron Cyclotron Resonance Ion Source (ECRIS). Existing radioactive beam facilities like REX‐ISOLDE or ISAC (TRIUMF) are already using charge state boosters for the post acceleration of radioactive ions. Upcoming facilities like the MSU re‐accelerator project, SPIRAL II, SPES, EURISOL and MATS within FAIR have identified the need of a breeding system, because of the demand for highly charged ions at low energies and due to the available budget. Charge state breeding with EBIS∕T devices requires several steps, which need to be optimized. A beam of singly charged ions must be prepared prior to injection into an EBIS∕T in order to match the acceptance of the electron beam. An efficient injection and short breeding times are required as well as a high abundance in one specific charge state, which can be manipulated in EBIS∕T devices. Further issues of charge breeder development are extraction and purification of the wanted highly charged ion species. The present paper will review the efforts of the EBIS∕T community and will give an overview of the planned and running facilities.

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28.52.-s	Fusion reactors
52.50.Qt	Plasma heating by radio-frequency fields; ICR, ICP, helicons
29.25.Rm	Sources of radioactive nuclei

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Review of Cluster Ion Beam Facilities and Technology

Isao Yamada and Noriaki Toyoda

AIP Conf. Proc. 1099, pp. 13-16; doi:http://dx.doi.org/10.1063/1.3119998 (4 pages)

Online Publication Date: 31 March 2009

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The paper reviews the development of cluster ion beam technology, including historical background, fundamental characteristics of cluster ion to solid surface interactions, emerging industrial applications, and identification of some of the significant events which occurred as the technology has evolved into what it is today. Processes employing ions of clusters comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster‐surface collisions produce important non‐linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals, and dielectrics, to assisted formation of thin films with nano‐scale accuracy, and to other surface modification applications.

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41.75.Cn	Negative-ion beams
36.40.-c	Atomic and molecular clusters
29.20.Ej	Linear accelerators

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Desorption of the NEG‐coated Aluminum Chamber

G. Y. Hsiung, C. M. Cheng, C. Y. Yang, C. K. Chan, and J. R. Chen

AIP Conf. Proc. 1099, pp. 17-20; doi:http://dx.doi.org/10.1063/1.3120008 (4 pages)

Online Publication Date: 31 March 2009

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The NEG‐coating, composed of ZrTiV with a lower temperature of activation, has been developed as a large surface getter pump for the aluminum (Al) chamber of small aperture and long length with a very poor conductance. However, the outgas of discharged gases, Ar or Kr, as well as the hydrocarbon molecules inside the NEG‐coated Al chamber has been observed. The desorption of the so‐called inert gases with heavier atomic mass residing inside the chamber results in the potential problem of higher cross section of scattering with the traveling beam hence reduces the life time seriously. To verify the outgas source of CH₄, the NEG‐coated Al‐chamber exposed with heavy water (D₂O) has been investigated. It shows the D₂O and methane are the only outgases from the non‐coated Al chamber exposed with D₂O. However, more outgas of CD_xH_y, CD₄, and the C₂D_xH_y complexes have been measured in the case of NEG‐coated Al chamber. Desorption of C₂D_xH_y molecules can be reduced by exposing the NEG‐coated surface with synchrotron radiation photons. The fact of beam cleaning effect verifies the source of C₂D_xH_y molecules are produced and desorbed from the NEG film. The NEG‐coated stainless steel (SS) chambers exposed with either D₂O or H₂O illustrate the similar results in the case of Al‐chambers. The dissociation of D₂O exposed on the NEG surface for both Al‐ and SS‐chambers are confirmed. The chemical compounds of C_mD_x and C_mD_xH_y are found produced and desorbed from the NEG‐coated after baking and activation.

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81.15.-z	Methods of deposition of films and coatings; film growth and epitaxy
81.65.Tx	Gettering

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Energy Loss And Beam Transport Properties of Gas Cluster Ion Beams

Noriaki Toyoda and Isao Yamada

AIP Conf. Proc. 1099, pp. 21-24; doi:http://dx.doi.org/10.1063/1.3120018 (4 pages)

Online Publication Date: 31 March 2009

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Energy losses of a gas cluster ion beam (GCIB) after collisions with residual gases were studied for Ar and CO₂ GCIBs. From the energy distribution of an Ar GCIB after collisions at various acceleration voltages and cluster sizes, it is found that GCIB lost its energy when its energy per atom was high. In addition, the energy loss of CO₂ GCIB was moderate compared to that of Ar GCIB at the same cluster size because of strong binging energy of CO₂ molecules. The energy loss mainly occurs as decrease of its cluster size. The number of the scattered atoms or molecules linearly increased with the energy per atom or molecule. The reduction of cluster size is determined by the energy∕atom and the cohesive energy of the gas.

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36.40.Wa	Charged clusters
29.20.Ej	Linear accelerators
33.15.Ry	Ionization potentials, electron affinities, molecular core binding energy

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Electron Cyclotron Resonance Ion Sources for Highly‐Charged Ion Beams

H. Koivisto

AIP Conf. Proc. 1099, pp. 25-30; doi:http://dx.doi.org/10.1063/1.3120028 (6 pages) | Cited 1 time

Online Publication Date: 31 March 2009

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Electron Cyclotron Resonance (ECR) ion sources are used for several different applications. Primarily they are used for the production of highly‐charged ion beams for nuclear physics experiments but they are also used, for example, in medical applications and radiation‐hardness tests of space electronics. Strong requests have been made from the nuclear physics community towards obtaining higher beam intensities and new exotic, even radioactive, ion beams. Due to the requirements more powerful ECR ion sources and new methods for the beam production are needed. In order to meet the beam intensity requirements several superconducting ion sources have recently been built or are under construction in Asia, Europe and the USA. The development work towards improvements in ion beam quality and the production of metal ion beams is also playing a crucial role. In this article a general overview concerning the ECR ion sources, their future and beam production will be given.

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52.50.Qt	Plasma heating by radio-frequency fields; ICR, ICP, helicons
29.25.Ni	Ion sources: positive and negative
29.20.Ej	Linear accelerators

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Accelerator System Development at High Voltage Engineering

M. G. Klein, A. Gottdang, R. G. Haitsma, and D. J. W. Mous

AIP Conf. Proc. 1099, pp. 31-34; doi:http://dx.doi.org/10.1063/1.3120041 (4 pages)

Online Publication Date: 31 March 2009

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Throughout the years, HVE has continuously extended the capabilities of its accelerator systems to meet the rising demands from a diverse field of applications, among which are deep level ion implantation, micro‐machining, neutron production for biomedical research, isotope production or accelerator mass spectrometry. Characteristic for HVE accelerators is the coaxial construction of the all solid state power supply around the acceleration tubes. With the use of solid state technology, the accelerators feature high stability and very low ripple. Terminal voltages range from 1 to 6 MV for HVE Singletrons and Tandetrons. The high‐current versions of these accelerators can provide ion beams with powers of several kW. In the last years, several systems have been built with terminal voltages of 1.25 MV, 2 MV and 5 MV. Recently, the first system based on a 6 MV Tandetron has passed the factory tests. In this paper we describe the characteristics of the HVE accelerator systems and present as example recent systems.

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29.20.Ej	Linear accelerators
29.25.Ni	Ion sources: positive and negative
82.80.Qx	Ion cyclotron resonance mass spectrometry

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Precise Fabrication of Silicon Wafers Using Gas Cluster Ion Beams

Hiromichi Isogai, Eiji Toyoda, Koji Izunome, Kazuhiko Kashima, Takafumi Mashita, Noriaki Toyoda, and Isao Yamada

AIP Conf. Proc. 1099, pp. 35-38; doi:http://dx.doi.org/10.1063/1.3120051 (4 pages)

Online Publication Date: 31 March 2009

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Precise surface processing of a silicon wafer was studied by using a gas cluster ion beam (GCIB). The damage caused to the silicon surface was strongly dependent on irradiation parameters. The extent of damage varied with the species of source gas and the acceleration voltage (Va) of cluster ions. It also varied with the cluster size and residual gas pressure. The influence of electron acceleration voltage (Ve) used for ionization of a neutral cluster was also investigated. The irradiation damage, such as an amorphous silicon (a‐Si) layer, a mixed layer of a‐Si and c‐Si (transition layer), and surface roughness, was increased with Ve. It is suggested that the increase in the amount of energy per atom was induced by high Ve, because of variation of the cluster size and∕or cluster charge. An undamaged smooth surface can be produced by Ar‐GCIB irradiation at low Ve and Va.

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41.75.Cn	Negative-ion beams
87.53.Bn	Dosimetry/exposure assessment
52.59.Bi	Grid- and ion-diode-accelerated beams

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Experimental Background Due To Particle Induced Gas Desorption In RHIC

S. Y. Zhang and D. Trbojevic

AIP Conf. Proc. 1099, pp. 39-41; doi:http://dx.doi.org/10.1063/1.3120061 (3 pages)

Online Publication Date: 31 March 2009

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Beam‐gas collision created experimental background, i.e., singles, has affected heavy ion and polarized proton operations in Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The gas molecules in interaction region are mainly caused by the electron induced gas desorption, and the electrons are produced from the beam induced electron multipacting, or called electron cloud. The background has a dependence on the usual electron cloud related parameters, such as the bunch intensity, bunch spacing, and the solenoid field. With the RHIC upgrade plan, the experimental background may become a luminosity limiting factor. Mitigations are discussed.

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29.27.-a	Beams in particle accelerators
29.20.-c	Accelerators
98.70.Vc	Background radiations

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A New High‐Current Proton Accelerator

M. R. Cleland, R. A. Galloway, L. DeSanto, and Y. Jongen

AIP Conf. Proc. 1099, pp. 42-45; doi:http://dx.doi.org/10.1063/1.3120067 (4 pages)

Online Publication Date: 31 March 2009

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A high‐current (>20 mA) dc proton accelerator is being developed for applications such as boron neutron capture therapy (BNCT) and the detection of explosive materials by nuclear resonance absorption (NRA) of gamma radiation. The high‐voltage dc accelerator (adjustable between 1.4 and 2.8 MeV) will be a single‐ended industrial Dynamitron® system equipped with a compact high‐current, microwave‐driven proton source. A magnetic mass analyzer inserted between the ion source and the acceleration tube will select the protons and reject heavier ions. A sorption pump near the ion source will minimize the flow of neutral hydrogen gas into the acceleration tube. For BNCT, a lithium target for generating epithermal neutrons is being developed that will be capable of dissipating the high power (>40 kW) of the proton beam. For NRA, special targets will be used to generate gamma rays with suitable energies for exciting nuclides typically present in explosive materials. Proton accelerators with such high‐current and high‐power capabilities in this energy range have not been developed previously.

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29.20.Ba	Electrostatic accelerators
24.30.-v	Resonance reactions
87.56.bd	Accelerators

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Advanced Surface Polishing For Accelerator Technology Using Ion Beams

Z. Insepov, J. Norem, A. Hassanein, and A. T. Wu

AIP Conf. Proc. 1099, pp. 46-50; doi:http://dx.doi.org/10.1063/1.3120076 (5 pages)

Online Publication Date: 31 March 2009

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A gas cluster ion beam (GCIB) technology was successfully applied to surface treatment of Cu, stainless steel, Ti, and Nb samples and to Nb rf‐cavities by using accelerated cluster ion beams of Ar, O₂ and combinations of them, with accelerating voltages up to 35 kV. DC field emission (dark current) measurements and electron microscopy were used to investigate metal surfaces treated by GCIB. The experimental results showed that GCIB technique can significantly reduce the number of field emitters and can change the structure of the Nb oxide layer on the surface. The RF tests of the GCIB‐treated Nb rf‐cavities showed improvement of the quality factor Q at 4.5 K. The superconducting gap was also enhanced by using the oxygen GCIB irradiation exposure.

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29.20.Ba	Electrostatic accelerators
07.77.Ka	Charged-particle beam sources and detectors
29.27.-a	Beams in particle accelerators

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The Bucharest FN Tandem Accelerator: Modernization and Development

S. Dobrescu, D. V. Mosu, D. Moisa, and S. Papureanu

AIP Conf. Proc. 1099, pp. 51-54; doi:http://dx.doi.org/10.1063/1.3120087 (4 pages)

Online Publication Date: 31 March 2009

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The Bucharest FN tandem accelerator, installed in 1973 and upgraded in 1983 to 9 MV, has been used for atomic and nuclear physics studies as well as for different applications using accelerated ion beams. In the last three years a program of modernization of the tandem accelerator including the replacement of the old accelerator equipment by new ones, installation of a pelletron system for the Van de Graaff generator and installation of new negative ion injectors was undertaken. In parallel a development of the tandem accelerator was started. In 2009, a beam pulsing system in the nanosecond range is scheduled to be installed. All these works aimed to transform the tandem accelerator in a reliable and efficient tool for research and applications are presented. The main lines of the research program at the Bucharest tandem accelerator are shortly presented too.

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29.20.Ba	Electrostatic accelerators
29.25.Ni	Ion sources: positive and negative
29.20.-c	Accelerators

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Development and Testing of Gallium Arsenide Photoconductive Detectors for Ultra Fast, High Dose Rate Pulsed Electron and Bremsstrahlung Radiation Measurements

George Kharashvili, Vakhtang Makarashvili, Marc Mitchell, Wendland Beezhold, Randy Spaulding, Douglas Wells, Thomas Gesell, and Wayne Wingert

AIP Conf. Proc. 1099, pp. 55-58; doi:http://dx.doi.org/10.1063/1.3120099 (4 pages)

Online Publication Date: 31 March 2009

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Real time radiation dose measurements are challenging in high dose rate environments such as those used for testing electronic devices or biological agents. Dosimetry needs in pulsed reactor fields and particle accelerator facilities require development of dosimeters with fast (10 s of picoseconds) response to pulsed radiation, linear response over a wide range of dose rates (up to 10¹¹ Gy/s), high resistance to radiation damage, and successful operation in mixed gamma and neutron environments. Gallium arsenide photoconductive detectors (GaAs PCD) have been shown to exhibit many of these desirable characteristics, especially fast time response. Less than 50 ps time resolution has been demonstrated when previously irradiated by fission neutrons. We have conducted a study of the response‐time dependence on neutron fluence, starting with fluences at ∼ 10¹⁴ n/cm². A 23‐MeV electron beam was used to produce photoneutrons in a tungsten target for irradiation of a GaAs wafer from which PCDs were made. The process was modeled using MCNPX computer code and the simulation results were compared to the experimental measurements. GaAs PCDs were fabricated from both neutron‐irradiated and non‐irradiated GaAs samples. The results of the preliminary tests of these devices in accelerator‐produced pulses of electron and bremsstrahlung radiation of various energies (13 to 35 MeV) and pulse lengths (100 ps to 4 μs) are presented together with an overview of the future plans of continuing GaAs PCD research at Idaho State University.

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87.53.Bn	Dosimetry/exposure assessment
29.25.Ni	Ion sources: positive and negative
07.89.+b	Environmental effects on instruments (e.g., radiation and pollution effects)

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Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

M. W. Francis and A. E. Ruggles

AIP Conf. Proc. 1099, pp. 59-62; doi:http://dx.doi.org/10.1063/1.3120109 (4 pages)

Online Publication Date: 31 March 2009

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The Spallation Neutron Source (SNS) is one of the largest science projects in the United States, with total cost near 1.4 Billion Dollars. The limiting factor of the facility had always been assumed to be the lifetime of the target window due to radiation damage. After further investigation, the lifetime of the target was determined not to be limited by radiation damage but by cavitation damage. The cavitation damage derives from pressure waves caused by the beam energy deposition. Vapor bubbles form when low to negative pressures occur in the mercury near the stainless steel target window due to wave interaction with the structure. Collapse of these bubbles can focus wave energy in small liquid jets that erode the window surface. Compressibility of the mercury can be enhanced to reduce the amplitude of the pressure wave caused by the beam energy deposition. To enhance compressibility, small (10 to 30 micron diameter) gas bubbles could be injected into the bulk of the mercury. Solubility and diffusivity parameters of inert gas in mercury are required for a complete mechanical simulation and engineering of these strategies. Using current theoretical models, one obtains a theoretical Henry coefficient of helium in mercury on the order of 3.9E15 Pa‐molHg∕molHe at 300 K. This low solubility was confirmed by a direct, offline experimental method. Mercury was charged with helium and any pressure change was recorded. Any pressure change was attributed to gas going into solution. Therefore, with the sensitivity of the experiment, a lower limit of 9E12 Pa‐molHg∕molHe was placed on the mercury‐helium system. These values guarantee a stable bubble lifetime needed within the SNS mercury target to mitigate cavitation issues.

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43.35.Ei	Acoustic cavitation in liquids
28.50.Ft	Fast and breeder reactors
29.25.Ni	Ion sources: positive and negative

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Time Of Flight Accelerator Mass Spectrometry (TOF‐AMS) of Large Molecular Ions at MeV Energies

J. A. M. Pereira, E. L. A. Macchione, S. S. Vasconcelos, N. Added, M. H. Tabacniks, O. Dietzsch, W. M. S. Santos, A. M. Luiz, and N. V. de Castro Faria

AIP Conf. Proc. 1099, pp. 63-65; doi:http://dx.doi.org/10.1063/1.3120118 (3 pages)

Online Publication Date: 31 March 2009

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The feasibility of using TANDEM electrostatic particle accelerators as a linear TOF analyzer for molecular ions (TOF‐AMS) is reported in this work. A specific ion source, based on a soft ionization technique commonly used in modern mass spectrometry, employing a pulsed UV‐laser to desorb molecular ions from the solid state, was built for that purpose. The current instrumentation has been used to analyze samples of CsI and C₆₀ using the whole accelerator as a linear Time of Flight spectrometer. From the point of view of basic studies on molecular collisions, the apparatus has some unique features that allow the simultaneous discrimination of various fragmentation and charge exchange channels for different types of molecular ions. From the point of view of applied studies, the TOF‐AMS technique may be able to overcome some difficulties encountered in mass spectrometry of biomolecules.

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29.20.Ej	Linear accelerators
07.75.+h	Mass spectrometers
29.20.Ba	Electrostatic accelerators

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Monte Carlo Simulation of the Irradiation of Alanine Coated Film Dosimeters with Accelerated Electrons

R. M. Uribe, F. Salvat, M. R. Cleland, and A. Berejka

AIP Conf. Proc. 1099, pp. 66-70; doi:http://dx.doi.org/10.1063/1.3120126 (5 pages)

Online Publication Date: 31 March 2009

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The Monte Carlo code PENELOPE was used to simulate the irradiation of alanine coated film dosimeters with electron beams of energies from 1 to 5 MeV being produced by a high‐current industrial electron accelerator. This code includes a geometry package that defines complex quadratic geometries, such as those of the irradiation of products in an irradiation processing facility. In the present case the energy deposited on a water film at the surface of a wood parallelepiped was calculated using the program PENMAIN, which is a generic main program included in the PENELOPE distribution package. The results from the simulation were then compared with measurements performed by irradiating alanine film dosimeters with electrons using a 150 kW Dynamitron™ electron accelerator. The alanine films were placed on top of a set of wooden planks using the same geometrical arrangement as the one used for the simulation. The way the results from the simulation can be correlated with the actual measurements, taking into account the irradiation parameters, is described. An estimation of the percentage difference between measurements and calculations is also presented.

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05.10.Ln	Monte Carlo methods
07.57.Kp	Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
87.53.Bn	Dosimetry/exposure assessment

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Performance of a Small High‐Pressure Xenon Detector at Sub‐MeV Photon Energies with an Example Application to Ion Beam Analysis

Arthur K. Pallone, Al Beyerle, and John D. Demaree

AIP Conf. Proc. 1099, pp. 71-74; doi:http://dx.doi.org/10.1063/1.3120139 (4 pages)

Online Publication Date: 31 March 2009

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Ion beam analysis (IBA) is a nondestructive method that provides nondestructive compositional information of a sample. Many IBA techniques derive the information from high‐energy photons produced by the interaction of the ion beam with the sample. The performance of a 1.53.8‐inch cm diameter by 37.6‐inch cm long high‐pressure xenon (HPXe) detector is investigated at photon energies useful to IBA. The results for the HPXe detector are then used to predict the performance of larger HPXe detectors at those energies and recommendations are made for an HPXe system for IBA.

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41.75.Cn	Negative-ion beams
07.85.Nc	X-ray and γ-ray spectrometers
81.70.-q	Methods of materials testing and analysis

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Development of a Portable 950 keV X‐band Linac for NDT

Takuya Natsui, Mitsuru Uesaka, Tomohiko Yamamoto, Fumito Sakamoto, Eiko Hashimoto, Lee Kiwoo, Naoki Nakamura, Masashi Yamamoto, Eiji Tanabe, Mitsuhiro Yoshida, Toshiyasu Higo, and Shigeki Fukuda

AIP Conf. Proc. 1099, pp. 75-78; doi:http://dx.doi.org/10.1063/1.3120148 (4 pages)

Online Publication Date: 31 March 2009

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We are developing a portable 950 keV X‐band (9.4 GHz) linac X‐ray source for on‐site nondestructive testing of erosion of metal pipes at a petrochemical complex. To develop it, we adopted a compact X‐band 9.4 GHz magnetron of 250 kW for RF generation device. The whole device, including power supply and cooling devices, were also downsized. The dose rate of X‐ray converted in a tungsten target is designed to be 0.2 Gy∕min at 1‐m distance. We designed an accelerating tube that uses the π mode for the lower energy part and the π∕2 mode cavity for the higher energy. We manufactured the accelerating tube and carried out beam acceleration tests, confirming that the electron beam was accelerated up to 950 keV.

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07.85.Fv	X- and γ-ray sources, mirrors, gratings, and detectors
81.70.-q	Methods of materials testing and analysis
29.20.Ej	Linear accelerators

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Compact LaBr₃: Ce Gamma Ray Detector with Si‐APD Readout

Jeremy Flamanc and Csaba Rozsa

AIP Conf. Proc. 1099, pp. 79-83; doi:http://dx.doi.org/10.1063/1.3120159 (5 pages) | Cited 1 time

Online Publication Date: 31 March 2009

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BrilLanCe 380™ (LaBr₃:Ce) crystal scintillators available from Saint‐Gobain Crystals have achieved 2.6% FWHM for 662 keV photons. This is accomplished with PMT light sensors. Attempts to have similarly good results with PIN photo‐diodes and APDs have not been successful. PIN photodiodes do not have any gain and the signal to noise ratio is poor at room temperature. Similarly, even though APDs have sufficient gain, they have poor signal to noise at room temperature. Recently there have been improvements in APDs decreasing the internal noise and increasing their sensitivity, making them an excellent light sensor. With the improved APD, it is now possible to achieve performance with a solid state light sensor comparable to that of PMTs. We have measured 2.8% for 662 keV gamma rays at room temperature using an APD for a light sensor on a 20 mm long crystal of 1.6 cc volume. APDs have advantages of compactness, inherent ruggedness and minimal sensitivity to magnetic fields. Such a device is very practical for hand held and portable field measurement applications. (Performance reported in SGC literature.)

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85.60.Dw	Photodiodes; phototransistors; photoresistors
29.40.Mc	Scintillation detectors
29.30.Kv	X- and γ-ray spectroscopy

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Characterization of a Fast Neutron Detection System With Large Angular Coverage and Granularity for Physics Studies and Applications

E. Chávez, L. Barrón‐Palos, Q. Curiel, R. Guerrero, A. Huerta, M. E. Ortiz, E. Moreno, G. Murillo, R. Policroniades, and A. Varela

AIP Conf. Proc. 1099, pp. 84-87; doi:http://dx.doi.org/10.1063/1.3120172 (4 pages)

Online Publication Date: 31 March 2009

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This work presents a review of fast neutron detection, with an emphasis on the use of plastic scintillating materials. We developed neutron detectors both at the Instituto de Física, UNAM and at the Tandem Accelerator Laboratory, ININ. We will describe in detail our detectors and their characteristics. We will present some results on the development of a large position‐sensitive neutron detector in two dimensions. In particular, we present a phenomenological formula that describes the complex dependence of the amount of light reaching a detector as a function of the position of the light source within the scintillating material. First measurements with a very small number of detectors are presented and show encouraging results.

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28.41.Rc	Instrumentation
29.40.Mc	Scintillation detectors
29.40.Gx	Tracking and position-sensitive detectors

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Radiation of X‐Rays Using Uniaxially Polarized LiNbO₃ Single Crystal

Shinji Fukao, Yoshikazu Nakanishi, Tadahiro Mizoguchi, Yoshiaki Ito, Toru Nakamura, and Shinzo Yoshikado

AIP Conf. Proc. 1099, pp. 88-91; doi:http://dx.doi.org/10.1063/1.3120182 (4 pages)

Online Publication Date: 31 March 2009

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X‐rays are radiated due to the bremsstrahlung caused by the collision of electrons with a metal target placed opposite the negative electric surface of a crystal by changing the temperature of a LiNbO₃ single crystal uniaxially polarized in the c‐axis direction. It is suggested that both electric field intensity and electron density determine the intensity of X‐ray radiation. Electrons are supplied by the ionization of residual gas in space, field emission from a case inside which a crystal is located, considered to be due to the high electric‐field intensity formed by the surface charges on the crystal, and an external electron source, such as a thermionic source. In a high vacuum, it was found that the electrons supplied by electric‐field emission mainly contribute to the radiation of X‐rays. It was found that the integrated intensity of X‐rays can be maximized by supplying electrons both external and by electric‐field emission. Furthermore, the integrated intensity of the X‐rays is stable for many repeated temperature changes.

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87.53.Bn	Dosimetry/exposure assessment
41.50.+h	X-ray beams and x-ray optics
68.37.Vj	Field emission and field-ion microscopy

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Neutron Yield With a Pulsed Surface Flashover Deuterium Source

G. Guethlein, S. Falabella, S. E. Sampayan, G Meyer, V. Tang, and P. Kerr

AIP Conf. Proc. 1099, pp. 92-94; doi:http://dx.doi.org/10.1063/1.3120194 (3 pages)

Online Publication Date: 31 March 2009

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As a step towards developing an ultra compact D‐D neutron source for various defense and homeland security applications, a compact, low average power ion source is needed. Towards that end, we are testing a high current, pulsed surface flashover ion source, with deuterated titanium as the spark contacts. Neutron yield and source lifetime data will be presented using a low voltage (<100 kV) deuterated target. With 20 ns spark drive pulses we have shown >10⁶ neutrons/s with 1 kHz PRF

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29.25.Dz	Neutron sources
29.25.Ni	Ion sources: positive and negative
52.80.Mg	Arcs; sparks; lightning; atmospheric electricity

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On‐site Real‐Time Inspection System for Pump‐impeller using X‐band Linac X‐ray Source

Tomohiko Yamamoto, Takuya Natsui, Hiroki Taguchi, Yoshihiro Taniguchi, Ki woo Lee, Eiko Hashimoto, Fumito Sakamoto, Akira Sakumi, Noritaka Yusa, Mitsuru Uesaka, Naoki Nakamura, Masashi Yamamoto, and Eiji Tanabe

AIP Conf. Proc. 1099, pp. 95-98; doi:http://dx.doi.org/10.1063/1.3120202 (4 pages)

Online Publication Date: 31 March 2009

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The methods of nondestructive testing (NDT) are generally ultrasonic, neutron, eddy‐current and X‐rays, NDT by using X‐rays, in particular, is the most useful inspection technique having high resolution. We can especially evaluate corroded pipes of petrochemical complex, nuclear and thermal‐power plants by the high energy X‐ray NDT system. We develop a portable X‐ray NDT system with X‐band linac and magnetron. This system can generate a 950 keV electron beam. We are able to get X‐ray images of samples with 1 mm spatial resolution. This system has application to real time impeller inspection because linac based X‐ray sources are able to generate pulsed X‐rays. So, we can inspect the rotating impeller if the X‐ray pulse rate is synchronized with the impeller rotation rate. This system has application in condition based maintenance (CBM) of nuclear plants, for example. However, 950 keV X‐ray source can only be used for thin tubes with 20 mm thickness. We have started design of a 3.95 MeV X‐band linac for broader X‐ray NDT application. We think that this X‐ray NDT system will be useful for corrosion wastage and cracking in thicker tubes at nuclear plants and impeller of larger pumps. This system consists of X‐band linac, thermionic cathode electron gun, magnetron and waveguide components. For achieving higher electric fields the 3.95 MeV X‐band linac structure has the side‐coupled acceleration structure. This structure has more efficient acceleration than the 950 keV linac with alternating periodic structure (APS). We adopt a 1.3 MW magnetron for the RF source. This accelerator system is about 30 cm long. The beam current is about 150 mA, and X‐ray dose rate is 10 Gy@1 m∕500 pps. In this paper, the detail of the whole system concept and the electromagnetic field of designed linac structure will be reported.

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81.70.Cv	Nondestructive testing: ultrasonic testing, photoacoustic testing
52.59.Px	Hard X-ray sources
81.70.Ex	Nondestructive testing: electromagnetic testing, eddy-current testing

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Characterization of a Surface‐Flashover Ion Source with 10–250 ns Pulse Widths

S. Falabella, G. Guethlein, P. L. Kerr, G. A. Meyer, J. D. Morse, S. Sampayan, and V. Tang

AIP Conf. Proc. 1099, pp. 99-101; doi:http://dx.doi.org/10.1063/1.3120212 (3 pages)

Online Publication Date: 31 March 2009

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As a step towards developing an ultra compact D‐D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. An electrochemically‐etched mask was used to define the electrode areas on the substrate during the sputtered deposition of the titanium films. Deuterium loading of the films was performed in an all metal‐sealed vacuum chamber containing a heated stage. Deuterium ion current from the source was determined by measuring the neutrons produced when the ions impacted a deuterium‐loaded target held at −90 kV. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns.

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29.25.Ni	Ion sources: positive and negative
52.80.Mg	Arcs; sparks; lightning; atmospheric electricity
81.15.Cd	Deposition by sputtering

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Proton Injector for CW‐Mode Linear Accelerators

Joseph D. Sherman, Donald Swenson, Frank Guy, Cody Love, Joel Starling, and Carl Willis

AIP Conf. Proc. 1099, pp. 102-105; doi:http://dx.doi.org/10.1063/1.3119989 (4 pages)

Online Publication Date: 31 March 2009

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Numerous applications exist for CW linear accelerators with final energies in the 0.5 to 4.0 MeV proton energy range. Typical proton current at the linac output energy is 20 mA. An important subsystem for the accelerator facility is a reliable dc mode proton injector. We present here design and laboratory results for a dc, 25‐keV, 30‐mA proton injector. The proton source is a 2.45‐GHz microwave hydrogen ion source which operates with an 875‐G axial magnetic field. Low emittance, high proton fraction (>85%), beams have been demonstrated from this source. The injector uses a novel dual‐solenoid magnet for matching the injector beam into a radio frequency quadrupole (RFQ) linear accelerator. Recently, a dc ion‐source development program has given up to 30 mA beam current. The dual solenoid is a compact and simple design utilizing tape‐wound, edge‐cooled coils. The low‐energy beam transport design as well as 25‐keV beam matching calculations to an RFQ will also be presented.

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29.25.Ni	Ion sources: positive and negative
29.20.Ba	Electrostatic accelerators
84.32.Hh	Inductors and coils; wiring

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