Design of the Advanced Rare Isotope Separator ARIS at FRIB Hausmann, M.; Aaron, A.M.; Amthor, A.M. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2013, Letnik:
317
Journal Article
Recenzirano
The Facility for Rare Isotopes Beams (FRIB) at Michigan State University will use projectile fragmentation and induced in-flight fission of heavy-ion primary beams at energies of 200MeV/u and higher ...and at a beam power of 400kW to generate rare isotope beams for experiments in nuclear physics, nuclear astrophysics, and fundamental symmetries, as well as for societal needs. The Advanced Rare Isotope Separator (ARIS) has been designed as a three-stage fragment separator for the efficient collection and purification of the rare isotope beams of interest. A vertically bending preseparator (first stage) with production target and beam dump is fully integrated into a production target facility hot cell with remote handling. The new separator compresses the accepted momentum width of up to ±5% of the beam by a factor of three in the standard operational mode. Provisions for alternate operational modes for specific cases are included in the design. This preseparator is followed by two, horizontally-bending separator stages (second and third stages) utilizing the magnets from the existing A1900 fragment separator at the National Superconducting Cyclotron Laboratory (NSCL). These stages can alternatively be coupled to a single high-resolution separator stage, resulting in the flexibility to optimize the operation for different experiments, including momentum tagging and in-flight particle identification of rare isotope beams. The design of ARIS will be presented with an emphasis on beam physics characteristics, and anticipated operational modes will be described.
Retrospective review.
Spinal cord injury is a known risk factor for bladder cancer. The risk of bladder cancer has been reported at 16-28 times higher than the general population. Earlier studies ...have identified indwelling catheters as risk factors. We examined the characteristics of bladder cancers in a spinal cord injury (SCI) population.
Long Beach VA Hospital Spinal Cord Injury Unit, Long Beach, California.
We reviewed SCI patients seen and diagnosed with bladder tumors between January 1983 and January 2007. Data collected included time since diagnosis, method of diagnosis, form of bladder management, pathologic type, treatment of the tumor, and outcome.
A total of 32 patients with bladder cancer were identified out of 1319 seen. Tumors found were 46.9% squamous cell carcinoma (SCC), 31.3% transitional cell carcinoma (TCC), 9.4% adenocarcinoma, and 12.5% mixed TCC and SCC. The primary form of bladder management was 44% urethral catheter for a mean of 33.3 years, 48% external catheter for a mean of 37.4 years, and 8% intermittent catheterization for a mean of 24.5 years. Nineteen patients had a known method of cancer detection with 42% found on screening cystoscopy.
The pathologic makeup of the tumors is similar to that reported earlier. Over 50% of patients diagnosed with bladder cancer in our population did not have an indwelling catheter. This suggests that the neurogenic bladder, not the indwelling catheter, may be the risk factor for bladder cancer. Urologists should consider diligent, long-term screening of all patients with SCI for bladder cancer and not just those with indwelling catheters.
Bladder management for male patients with spinal cord injury (SCI) challenges the urologist to work around physical and social restrictions set forth by each patient. The objective of this study was ...to compare the complications associated with urethral catheter (UC) versus suprapubic tube (SPT) in patients with SCI.
A retrospective review of records at Long Beach Veterans Hospital was carried out to identify SCI patients managed with SPT or UC. Chart review identified morbidities including urinary tract infection (UTI), bladder stones, renal calculi, urethral complications, scrotal abscesses, epididymitis, gross hematuria and cancer. Serum creatinine measurements were evaluated to determine whether renal function was maintained.
In all, 179 patients were identified. There was no significant difference between the two catheter groups in any areas in which they could be compared. There were catheter-specific complications specific to each group that could not be compared. These included erosion in the UC group and urethral leak, leakage from the SPT and SPT revision in the SPT group. Average serum creatinine for the UC and SPT groups was 0.74 and 0.67 mg per 100 ml, respectively.
SCI patients with a chronic catheter have similar complication rates of UTIs, recurrent bladder/renal calculi and cancer. Urethral and scrotal complications may be higher with UC; however, morbidity from SPT-specific procedures may offset benefits from SPT. Serum creatinine was maintained in both groups. Overall, bladder management for patients with chronic indwelling catheters should be selected on the basis of long-term comfort for the patient and a physician mind-set that allows flexibility in managing these challenges.
The radiation damage model in the Particle and Heavy Ion Transport code System (PHITS) uses screened Coulomb scattering to evaluate the energy of the target primary knock-on atom (PKA) created by the ...projectile and the “secondary particles,” which include all particles created from the sequential nuclear reactions. We investigated the effect of nuclear reactions on displacement per atom (DPA) values for the following cases using a copper target: (1) 14 and 200MeV proton incidences, (2) 14 and 200MeV/nucleon 48Ca incidences, and (3) 14 and 200MeV and reactor neutrons incidences. For the proton incidences, the ratio of partial DPA created by protons to total decreased with incident proton energy and that by the secondary particles increased with proton energy. For 48Ca beams, DPA created by 48Ca is dominant over the 48Ca range. For the 14 and 200MeV neutron incidences, the ratio of partial DPA created by the secondary particles increases with incident neutron energy. For the reactor neutrons, copper created by neutron–copper nuclear elastic scattering contributes to the total DPA. These results indicate that inclusion of nuclear reactions and Coulomb scattering are necessary for DPA estimation over a wide energy range from eV to GeV.
The radiation damage model in the PHITS (Particle and Heavy Ion Transport code System) has been improved using the screened Coulomb scattering to evaluate the energy of the target PKA (Primary Knock ...on Atom) created by the projectile and the “secondary particles” which include all particles created from the sequential nuclear reactions. For the reactions between 130MeV/u 76Ge ions and tungsten, DPA (Displacement per Atom) values calculated with the improved PHITS are in good agreement with SRIM results, which does not treat nuclear reactions. For the high-energy proton and 3He incident reactions, a target PKA created by the “secondary particles” was more dominant than a target PKA created by the projectile in DPA calculations. Therefore, the improved PHITS can calculate DPA values at high energies and SRIM leads to severe underestimation where projectile energy is high enough to create nuclear reactions. For 1.1 and 1.94GeV proton incidences, resulting displacement cross sections with the defect production efficiency were in better agreement with the experimental data than cross sections calculated without the defect production efficiency. Thus improved PHITS is applicable to evaluate the displacement cross sections for the various particles and over a wide energy range and to calculate DPA values determined by different particles and fluxes in an irradiation environment.
The purpose of the study is to obtain estimates of limits on uncontrolled beam losses of heavy ions for allowing hands-on maintenance at a heavy-ion linac for a rare isotope beam facility. ...Semiempirical formulas are used to estimate dose equivalent rates from activated accelerator components for 1 W/m uncontrolled losses of protons up to 1 GeV. The estimated dose rates after a 100-day irradiation time, 4-h postshutdown cooling time are compared to a hands-on maintenance limit of 1 mSv/h (100 mrem/h) at 30 cm. The transport codes PHITS and MCNP5 and activation code DCHAIN-SP 2001 are used to verify the estimate for proton losses and to obtain limits on heavy-ion beam losses that will satisfy the hands-on maintenance dose rate limit.
It has been sometimes necessary for personnel to work in areas where low-energy heavy ions interact with targets or with beam transport equipment and thereby produce significant levels of radiation. ...Methods to predict doses and to assist shielding design are desirable. The Particle and Heavy Ion Transport code System (PHITS) has been typically used to predict radiation levels around high-energy (above 100 MeV amu(-1)) heavy ion accelerator facilities. However, predictions by PHITS of radiation levels around low-energy (around 10 MeV amu(-1)) heavy ion facilities to our knowledge have not yet been investigated. The influence of the "switching time" in PHITS calculations of low-energy heavy ion reactions, defined as the time when the JAERI Quantum Molecular Dynamics model (JQMD) calculation stops and the Generalized Evaporation Model (GEM) calculation begins, was studied using neutron energy spectra from 6.25 MeV amu(-1) and 10 MeV amu(-1) (12)C ions and 10 MeV amu(-1) (16)O ions incident on a copper target. Using a value of 100 fm c(-1) for the switching time, calculated neutron energy spectra obtained agree well with the experimental data. PHITS was then used with the switching time of 100 fm c(-1) to simulate an experimental study by Ohnesorge et al. by calculating neutron dose equivalent rates produced by 3 MeV amu(-1) to 16 MeV amu(-1) (12)C, (14)N, (16)O, and (20)Ne beams incident on iron, nickel and copper targets. The calculated neutron dose equivalent rates agree very well with the data and follow a general pattern which appears to be insensitive to the heavy ion species but is sensitive to the target material.
Data on neutron dose attenuation by thick concrete, cast iron, and cast iron plus concrete composite shields for heavy ions and protons having high energies (200–1000
MeV/u) are necessary for ...shielding designs of high-powered heavy ion accelerator facilities. Neutron production source terms, shield material attenuation lengths, and neutron dose rate reduction effectiveness of the bulk shielding in the angular range from 0° to 125° were determined by the Particle and Heavy Ion Transport Code (PHITS) for beams of 300 and 550
MeV/u
48Ca ions, 200 and 400
MeV/u
238U ions, 800
MeV/u
3He and 1
GeV protons. Calculated results of interaction lengths of concrete and cast iron were also compared with similar work performed by Agosteo et al., and to experimental and other calculated data on interaction lengths. The agreement can be regarded as acceptable.
Secondary neutron-production cross sections have been measured from interactions of 290 MeV/nucleon C and 600 MeV/nucleon Ne in a target composed of simulated Martian regolith and polyethylene, and ...from 400 MeV/nucleon Ne interactions in wall material from the International Space Station. The data were measured between 5 deg. and 80 deg. in the laboratory. We report the double-differential cross sections, angular distributions, and total neutron-production cross sections from all three systems. The spectra from all three systems exhibit behavior previously reported in other heavy-ion neutron-production experiments, namely, a peak at forward angles near the energy corresponding to the beam velocity, with the remaining spectra generated by pre-equilibrium and equilibrium processes. The double-differential cross sections are fitted with a moving-source parametrization. Also reported are the data without corrections for neutron flux attenuation in the target and other intervening materials and for neutron production in nontarget materials near the target position. These uncorrected spectra are compared with SHIELD-HIT and PHITS transport model calculations. The transport model calculations reproduce the spectral shapes well but, on average, underestimate the magnitudes of the cross sections.
Results of a first investigation of the response of gallium nitride nanowires to high-Z heavy ion irradiation are reported. Pre-irradiation characterization of the gallium nitride nanowires used in ...these experiments showed that that they had a two-phase coaxial structure, consisting of an outer shell of zinc–blende-phase gallium nitride and a coaxial core of wurtzite-phase gallium nitride. Observed radiation interactions with the two-phase structure are reported. A nanowire-based field effect transistor using these GaN nanowires showed normal real-time operation during irradiation by Krypton-78 heavy ions under high bias conditions.
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