Low Energy Accelerator Facility Research Articles

Imaging and dosimetric characteristics of 67 Cu

In recent years the use of beta-emitting radiopharmaceuticals for cancer therapy has expanded rapidly following development of therapeutics for neuroendocrine tumors, prostate cancer, and other oncologic malignancies. One emerging beta-emitting radioisotope of interest for therapy is 67Cu (t1/2: 2.6 d) due to its chemical equivalency with the widely-established positron-emitting isotope 64Cu (t1/2: 12.7 h). In this work we evaluate both the imaging and dosimetric characteristics of 67Cu, as well as producing the first report of SPECT/CT imaging using 67Cu. To this end, 67Cu was produced by photon-induced reactions on isotopically-enriched 68Zn at the Low-Energy Accelerator Facility (LEAF) of Argonne National Laboratory, followed by bulk separation of metallic 68Zn by sublimation and radiochemical purification by column chromatography. Gamma spectrometry was performed by efficiency-calibrated high-purity germanium (HPGe) analysis to verify absolute activity calibration and establish radionuclidic purity. Absolute activity measurements corroborated manufacturer-recommended dose-calibrator settings and no radionuclidic impurities were observed. Using the Clinical Trials Network anthropomorphic chest phantom, SPECT/CT images were acquired. Medium energy (ME) SPECT collimation was found to provide the best image quality from the primary 185 keV gamma emission of 67Cu. Reconstructed images of 67Cu were similar in quality to images acquired using 177Lu. Recovery coefficients were calculated and compared against quantitative images of 99mTc, 177Lu, and 64Cu within the same anthropomorphic chest phantom. Production and clinical imaging of 67Cu appears feasible, and future studies investigating the therapeutic efficacy of 67Cu-based radiopharmaceuticals are warranted.

Measurement and simulation of gamma-ray background in a low energy accelerator facility

The γ-ray background in the indoor environment has been measured up to 3 MeV to evaluate the feasibility of studying low cross-section (nanobarn to picobarn range) astrophysical reactions at the Facility for Research in Experimental Nuclear Astrophysics (FRENA), Saha Institute of Nuclear Physics, Kolkata. An n-type coaxial HPGe detector with 20% relative efficiency has been placed at different locations in the accelerator and beam halls for the measurement. The measured activity has been compared with that at two laboratories (with standard brick walls) with and without passive and active radiation shieldings. As the halls at FRENA are well shielded by concrete, the contribution of the shielding in indoor γ-ray background has been delineated by simulation using a 4π-geometry model.

DESIGN AND BEAM COMMISSIONING OF THE LEAF-RFQ

An 81.25 MHz continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed and fabricated for the Low Energy Accelerator Facility (LEAF) by the Institute of Modern Physics (IMP) of the Chinese Academy of Science (CAS). The operation frequency is 81.25 MHz and the inter-vane voltage is a constant of 70 kV. It took about 44 hours continuous conditioning to reach RF power of 75 kW which is 1.1 time of the maximum designed value, and the successful CW acceleration of 150 eµA He+ beam to the designed energy of 0.5 MeV/u was already done. The results of the low power test, the RF conditioning and the beam acceleration will be reported in this paper.

Characterization of the new hybrid low-energy accelerator facility in Mexico

In 2013, a new accelerator mass spectrometry (AMS) facility was inaugurated in Mexico. Since then a substantial number of precise measurements of low concentrations of radioactive isotopes (14C, 10Be, 26Al and Pu) have been made. This paper describes the extension to the isotope separator installed at the end of 2017. It takes advantage of the 1MV High Voltage Engineering Europa (HVEE) tandem accelerator with the multicathode ion source (MCIS) and the fine-tuned injection system which delivers low-energy beams into a multipurpose scattering chamber. The MCIS allows for a quick and smooth change of the ion species to be accelerated. The ability to automatically tune all the optics in the injection system produces an accelerator laboratory that can change the beam species, intensities and energies in a few seconds. The careful and detailed study of the high-energy analyzing magnet using well-known proton resonances in 12C and 28Si, allowed for a calibration of the terminal voltage and beam energy. Stable ion beams with energies as low as 300 keV and as high as 8 MeV, from H to Fe, and with intensities in the range 109-1015 particles per second, were produced as listed.

Development and beam commissioning of a continuous-wave four-vane heavy ion radio-frequency quadrupole accelerator based on stable operation

Abstract A continuous-wave (CW) heavy ion radio frequency quadrupole (RFQ) accelerator was developed for the Low Energy Accelerator Facility (LEAF) at IMP. The RFQ accelerator is the most effective accelerator for accelerating the low energy high intensity beam, but there are challenges achieving the stable CW operation. This paper presents the development of the LEAF RFQ based on the stable CW operation. In the beam dynamics design, a multi-harmonic buncher is utilized to reduce the longitudinal emittance and the constant-voltage design is applied for low RF power loss. In the radio frequency (RF) design, the constant-voltage four-vane RFQ is selected to reduce the power dissipation. The π -mode stabilizing loop (PISL) is employed to reduce the admixture of the dipole field. In order to ensure the stability of the cavity structure, the multi-physics of the cavity are analysed. The resonant frequency sensitivities of the cooling water temperature are studied to tune the cavity frequency during operation. Through low power test and tuning, the resonance frequency and field distributions are optimized. The beam commissioning ( 4He 1 + , 14N 2 + and 86Kr 13 + ) and some radiation experiments have been performed. The entire processes of the LEAF RFQ development, such as, beam dynamics design, RF design, multi-physics analysis, low power test, high power conditioning, beam commissioning and some radiation experiments, will be detailed presented in this paper. The results of testing and commissioning indicate that the development of the LEAF RFQ has succeeded. And the design scheme for RFQ with stable CW operation in this work can be applied to other future CW RFQs.

The design and fabrication of 81.25 MHz RFQ for Low Energy Accelerator Facility

Abstract To provide high shunt impendence with low power losses, an 81.25 MHz continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed and machined as parts of the Low Energy Accelerator Facility (LEAF). In this paper, the mechanical structure and the main processing technology of the RFQ cavities are described according to the physical and geometric parameters requirements of the RFQ. The fabrication of the RFQ has been completed and the test results agree well with the design requirements. The RFQ accelerator will work in Institute of Modern Physics, Chinese Academy of Sciences in 2018.

Three-dimensional multi-physics analysis and commissioning frequency tuning strategy of a radio-frequency quadrupole accelerator

The resonant frequency stability of the radio frequency quadrupole (RFQ) is an important concern during commissioning. The power dissipated on the RFQ internal surface will heat the cavity and lead to a temperature rise and a structural deformation, especially in the continuous wave (CW) RFQs, which will cause the resonant frequency shifts. It is important to simulate the temperature rise, the deformation and the frequency shift of the RFQ cavity. The cooling water takes away the power to maintain the frequency stability. Meanwhile, the RFQ resonant frequency can be tuned by adjusting the water temperature. In this paper, a detailed three-dimensional multi-physics analysis of the Low Energy Accelerator Facility (LEAF) RFQ will be presented and a commissioning frequency tuning strategy will be studied.

Design of an 81.25 MHz continuous-wave radio-frequency quadrupole accelerator for Low Energy Accelerator Facility

An 81.25MHz continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed for the Low Energy Accelerator Facility (LEAF) at the Institute of Modern Physics (IMP) of the Chinese Academy of Science (CAS). In the CW operating mode, the proposed RFQ design adopted the conventional four-vane structure. The main design goals are providing high shunt impendence with low power losses. In the electromagnetic (EM) design, the π-mode stabilizing loops (PISLs) were optimized to produce a good mode separation. The tuners were also designed and optimized to tune the frequency and field flatness of the operating mode. The vane undercuts were optimized to provide a flat field along the RFQ cavity. Additionally, a full length model with modulations was set up for the final EM simulations. Following the EM design, thermal analysis of the structure was carried out. In this paper, detailed EM design and thermal simulations of the LEAF-RFQ will be presented and discussed. Structure error analysis was also studied.

Air-Induced Recovery of Proton-Exposed Space Materials

T HE fact that materials degrade in space-radiation environments has been studied for decades [1–19] and continues to be an issue of significant importance for space-based systems. Consequently, ground-based simulation of space environmental effects remains an invaluable method for ensuring the performance of any orbital asset, particularly as newmaterials, coatings, and processes are introduced. High-fidelity simulation of space environmental effects requires accurate definition and modeling of the orbital mission exposure, appropriate calculation of the absorbed radiation dose as a function of material thickness, proper simulation of this dose-depth profile in the laboratory, and precise characterization of test-induced changes in material properties. When performing material characterization, in vacuomeasurements are absolutely essential to avoid atmospheric effects on tested materials. Failure to do this can lead to results that are skewed by the too-often-overlooked dynamic of air-induced recovery of radiation-induced degradation, also known as bleaching. For some materials, ignoring the effects of bleaching can easily lead to a significant under estimation of radiation-induced losses and an inaccurate prediction of on-orbit performance. Bleaching is known to occur primarily for thermal control materials [20], and recent work by The Aerospace Corporation has added to the evidence that somematerials, which have been degraded from exposure to simulated space environments, display air-induced recovery behavior. In particular, samples of silverized Teflon, aluminized Kapton, and Z-93P ceramic white paint that were exposed to simultaneous ultraviolet (UV) and electron radiation in a test designed to simulate the conditions present at geosynchronous Earth orbit (GEO) exhibited noticeable bleaching upon subsequent exposure to air. In each case, a portion of the test-induced optical losses was recovered after a brief period ( 2 min) of air exposure. The behavior is material-specific, exhibiting differences in affected spectral region and magnitude of change. The recovery can occur rapidly or over long timescales, with the rate of recovery appearing to depend on material porosity and/or ambient temperature. The spectral response of the three materials is exemplified in Fig. 1. Although air-induced bleaching of optical degradation in some thermal control materials is relatively common, and the effect is not typically observed for materials that are more resistant to the effects of space-radiation exposure, such as solar-cell coverglass.Additional data generated by The Aerospace Corporation, however, indicated that certain coated coverglass materials, namely, those with thin-film coatings of magnesium fluoride (MgF2) and indium tin oxide (ITO), might also be susceptible to bleaching. In another recent GEO simulation, samples of MgF2/ITO-coated 0214 coverglass (0214 refers to the manufacturer-specific type of coverglass substrate) exhibited slight, yet discernible, air-induced recovery of spectral transmittance following simultaneous exposure to UV and electron radiation. Figure 2 shows the material’s spectral response to a short ( 2 min) postirradiation air exposure. Primarily, because of facility limitations, proton exposures at The Aerospace Corporation historically have been performed, usually precedingUV/electron irradiation, in a separate exposure facility: the low-energy accelerator facility (LEAF). The LEAF has a vacuum chamber attached to a linear ion accelerator; the accelerator’s beam is passed through a 30 deg magnetic turn to select the appropriate ion species, and the beam is rastered across the exposure target. The LEAF lacks in vacuo optical measurement capability; thus, air exposure is unavoidable when characterizing proton-induced material changes. Because of this, it is unknown whether, or to what degree, bleaching occurs for proton-irradiated coverglass materials, although it seems reasonable to suspect that somematerials degraded by proton exposure would also exhibit air-induced recovery. Given the apparent bleaching ofUV/electron-induced degradation in MgF2/ITO-coated coverglass and the lack of in vacuo optical measurement capability of the LEAF, this research effort was undertaken to investigate the air-induced response of protonirradiated space materials. Making this possible is The Aerospace Corporation’s newest space environmental effects exposure facility, which had already possessed in vacuo optical measurement capability and now features a variable-energy proton flood gun. This recently enhanced facility makes possible measurements of protonirradiated materials that are free from atmospheric effects and allows Received 21 September 2011; revision received 5 December 2011; accepted for publication 9 January 2012. Copyright © 2012 by The Aerospace Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0022-4650/12 and $10.00 in correspondence with the CCC. Research Scientist, Materials Science Department, Space Materials Laboratory, 2310 East El Segundo Boulevard, M2-248. Distinguished Scientist, Space Materials Laboratory, 2310 East El Segundo Boulevard, M2-248. JOURNAL OF SPACECRAFT AND ROCKETS Vol. 49, No. 4, July–August 2012

The Data Acquisition and Analysis Complex for the BNL Low Energy Accelerator Facility

The Data Acquisition and Analysis Complex is based on an SDS Sigma-7 computer with special purpose hardware. This complex will be time-shared by users at four independent accelerators. Each user may perform computations or data analysis while simultaneously collecting data and displaying results. A special feature of this complex is that the displays, programs and data are maintained on disc memories thus freeing the central processor and core memory for independent time-sharing tasks.