Indiana University Cyclotron Facility Research Articles

Evaluation and Application of U.S. Medical Proton Facilities for Single Event Effects Test

We present the challenges of using new medical proton therapy cyclotrons for SEE tests in the 200 MeV regime. Solutions are discussed to utilize these facilities as a replacement for the Indiana University Cyclotron Facility. Part data response to conventional scattered proton beams are compared to newer scanning beam configurations. A common dosimetry system for independent determination of fluence and beam uniformity is presented.

RADIATION HARDNESS STUDIES OF InGaAs AND Si PHOTODIODES AT 30, 52, & 98 MeV AND FLUENCES TO 5 × 1011 PROTONS/CM2

Here we report the results of an investigation into the effects of ionizing radiation on commercial off-the-shelf InGaAs and Si photodiodes. The photodiodes were exposed to 30, 52, and 98 MeV protons with fluences ranging from 108 - 5 × 1011 protons/cm2 at the Indiana University Cyclotron Facility. We tested the photodiodes for changes to their dark current and their relative responsivity as a function of wavelength. The Si photodiodes showed increasing damage to their responsivity with increasing fluence; the InGaAs photodiodes showed significantly increased dark current as the fluence increased. In addition, we monitored the absolute responsivity of the InGaAs photodiodes over their entire bandpass. Our measurements showed no evidence for broadband degradation or graying of the response at the fluences tested. All measurements in this investigation were made relative to detectors traceable to NIST standards.

Surgical organ displacement for proton radiotherapy

Proton radiotherapy is a method of applying high-energy particle radiation to treat cancers. Proton therapy is appealing due to its ability to deliver highly conformal dose distributions while minimizing radiation to adjacent normal tissues (1). Proton treatments first began in the 1950s using equipment added on to large nuclear physics labs. The Indiana University Health Proton Therapy Center (IUHPTC, formerly Midwest Proton Radiotherapy Institute) was built at the Indiana University Cyclotron Facility in Bloomington, Indiana, and was the third established center actively treating patients in the United States. At present, there are 10 proton centers treating patients in the US and several more around the world.

Performance characteristics and long-term calibration stability of a beam monitor for a proton scanning gantry

Abstract A monitor for a uniformly scanned beam was designed and constructed by the Indiana University Cyclotron Facility for use in a clinical proton gantry at the Midwest Proton Radiotherapy Institute. The beam monitor is a thin-walled, wide-aperture ionization chamber, which provides information about dose, beam size, symmetry, flatness, and position. Several characteristics of the monitor’s performance were studied, including linearity in dose rate, reproducibility, recombination correction, and dependence on both radiation field size and gantry angle. Additionally, stability of the detector output was analyzed using daily monitor calibrations performed over a period of 21 months. The beam monitor was found to meet design requirements for linearity (±1%), calibration stability (±2%), and stability of response as a function of gantry angle (±1%). Beam monitor calibration statistics also revealed a sine-like yearly trend with a ±2% maximum deviation from the average. These and other beam monitor test results are presented and discussed in the context of the detector design. Design changes aimed at further improving the detector’s performance characteristics are proposed.

Measurements of the neutron brightness from a phase II solid methane moderator at the LENS neutron source

Measurements of the neutron brightness from a solid methane moderator were performed at the Low Energy Neutron Source (LENS) at the Indiana University Cyclotron Facility (IUCF) to characterize the source and to test our new neutron scattering model of phase II solid methane [1]. A time-of-flight method was used to measure the neutron energy spectrum from the moderator in the energy range of 0.1 meV ∼ 1 eV . Neutrons were counted with a high efficiency 3He detector. The solid methane in the moderator occupied phase II and the energy spectra were measured at 20 K and 4 K. We tested our newly developed scattering kernels for phase II solid methane by calculating the neutron brightness expected from the methane moderator at the LENS neutron source using MCNP (Monte Carlo N-particle Transport Code). Within the accuracy of our approximate approach, our model correctly predicts the neutron brightness at both temperatures.

Introducing New Technology into the Clinic: The First Year of Experience in Proton Therapy with a Uniform Scanning System

The introduction of new and unique technology into routine clinical practice needs critical attention to its functionality and constant improvement. We wish to summarize some parameters relevant to clinical practice from our experience of the first year of clinical operation of a treatment room with a unique proton beam scanning system at the Midwest Proton Radiotherapy Institute (MPRI) constructed by Indiana University Cyclotron Facility.

ACORN: An experiment to measure the electron–antineutrino correlation in neutron decay

The aCORN experiment is designed to make a precision ( < 1 % ) measurement of the electron–antineutrino angular correlation ( a-coefficient) in neutron beta decay. It uses a new method proposed in 1996 by Yerozolimsky and Mostovoy. Electrons and recoil protons from neutron decay in a cold beam are detected in coincidence. The momenta of the particles are selected so that the protons form two kinematically distinct time-of-flight groups as a function of electron energy. The count rate asymmetry in these two groups is proportional to the a-coefficient. Precision spectroscopy of the protons is not required. The apparatus is currently under construction. It will be integrated and tested at the Indiana University Cyclotron Facility (IUCF) and then moved to the NIST Center for Neutron Research for the initial physics run.

Neutronic design and measured performance of the Low Energy Neutron Source (LENS) target moderator reflector assembly

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 ms ) 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.

The Indiana Cooler: A Retrospective

From 1983 to 2002, the Indiana Cooler was constructed and operated at the Indiana University Cyclotron Facility. During that period, a relatively small group of people built an accelerator complex, explored the new technology of electron cooling, and demonstrated its usefulness in nuclear and particle physics. This review recounts the history of the project, describes the facility, and summarizes the scientific results in atomic, nuclear, and particle physics, and in the physics of beams.

Multichannel detectors for profile measurements in clinical proton fields

Two beam profile measurement detectors have been developed at Indiana University Cyclotron Facility to address the need for a tool to efficiently verify dose distributions created with active methods of clinical proton beam delivery. The multipad ionization chamber (MPIC) has 128 ionization chambers arranged in one plane and is designed to measure lateral profiles in fields up to 38 cm in diameter. The MPIC pads have a 5 mm pitch for fields up to 20 cm in diameter and a 7 mm pitch for larger fields, providing the accuracy of field size determination about 0.5 mm. The multilayer ionization chamber (MLIC) detector contains 122 small-volume ionization chambers stacked at a 1.82 mm step (water-equivalent) for depth-dose profile measurements. The MLIC detector can measure profiles up to 20 cm in depth, and determine the 80% distal dose fall-off with about 0.1 mm precision. Both detectors can be connected to the same set of electronics modules, which comprise the detectors' data acquisition system. The detectors have been tested in clinical proton fields produced with active methods of beam delivery such as uniform scanning and energy stacking. This article describes detector performance tests and discusses their results. The test results indicate that the MPIC and MLIC detectors can be used for dosimetric characterization of clinical proton fields. The detectors offer significant time savings during measurements in actively delivered beams compared with traditional measurements using a water phantom.

LENS: A new university-based neutron source for science and education

The low-energy neutron source (LENS) is currently under construction at the Indiana University Cyclotron Facility. LENS is a long-pulse neutron source utilizing low-energy (p,xn) reactions on a beryllium target to produce neutrons. There are several unique features of the LENS facility. The low proton beam energy of 13MeV results in a low heat load on the moderator system, enabling the operation of the moderator at temperatures lower than 10K. The low beam energies also result in relatively low activation of the materials surrounding the target and moderator, thus enabling rapid prototyping and turnaround times for a moderator studies program.

Microwave proton sources for the IUCF LENS project

The Indiana University Cyclotron Facility (IUCF) has constructed and placed in operation a Low Energy Neutron Source using a 10mA, 7MeV proton beam incident on a beryllium target. A microwave ion source used for the IUCF cyclotrons was modified to work in this application. In parallel, a 150mA, 75keV injector, based on the same ion source technology, is under construction. This higher current injector will be used to inject beam into a new 100mA peak current linac that will be installed in 2006. The simulations of the 75keV injector are reported.

LENS: A New Pulsed Neutron Source for Research and Education.

A new pulsed neutron source is under construction at the Indiana University Cyclotron Facility (IUCF). Neutrons are produced via (p,n) reactions by a low-energy proton beam incident on a thin beryllium target. The source is tightly coupled to a cold methane moderator held at a temperature of 20 K or below. The resulting time-averaged cold neutron flux is expected to be comparable to that of the Intense Pulsed Neutron Source (IPNS) facility at Argonne National Laboratory. The initial experimental suite will include instrumentation for small angle neutron scattering (SANS), moderator studies, radiography, and zero-field spin-echo SANS.

LENS—a pulsed neutron source for education and research

At the Indiana University Cyclotron Facility construction of a new source of cold neutrons has begun. Neutrons are generated by stopping 13 MeV protons in a beryllium target, located at the center of a moderator structure. Cold neutrons are emitted from a slab of frozen methane. Three beam lines deliver neutrons for scattering experiments, radiography and moderator studies. The purpose of the project is to develop a low-cost, small-scale facility, suitable for a university or an industrial setting, to provide a testing ground of instrumentation destined for use at a larger facility, to improve awareness of the use of neutron probes in a wide range of applications, and to offer a training opportunity for future neutron physicists.

A fast low-noise charged-particle CVD diamond detector

This work presents the design and test results of a charged-particle solid-state detector with ultrafast signal response based on polycrystalline chemical-vapor-deposition (pCVD) diamond as active detector material and a high-bandwidth RF amplifier. We tested the detector at the Indiana University Cyclotron Facility Bloomington, IN, in a proton beam with a kinetic energy ranging from 55 to 200 MeV. The detector signals showed an average pulsewidth of 1.38 ns, which enables single-particle counting at instantaneous rates approaching the gigahertz range. The detector operated with a signal-to-noise ratio of 7 : 1 for 200-MeV protons and a single-particle detection efficiency up to 99%.

A continuous wave microwave proton source and low energy beam transport for the IUCF cyclotrons

A high reliability and low maintenance proton injector for a 20–750 keV cw radio frequency quadrupole (RFQ) has been constructed and installed to supply beam for acceleration to 208 MeV by the Indiana University Cyclotron Facility cyclotrons. The injector includes a 6 mA 2.45 GHz microwave proton source, two solenoids to match the 20 keV beam to the RFQ, a third pulsed solenoid for modulating the beam intensity out of the RFQ and an electrostatic chopper that operates at 17.79 MHz to select only the beam that will match the rf phase acceptance of the 35.58 MHz cyclotrons. The injector has been nearly continuous and with no failures since June 2003.

Beam Properties of the new Radiation Effects Research Stations at Indiana University Cyclotron Facility

ABSTRACTWe describe two new beamlines for radiation effects research at the Indiana University Cyclotron Facility. Protons with energies up to 205 MeV are available. One of the beamlines offers momentum selected beams at energies as low as 52 MeV.

First spin flipping of a stored spin-1 polarized beam.

We recently studied spin flipping of a 270 MeV vertically polarized deuteron beam stored in the Indiana University Cyclotron Facility Cooler Ring. We adiabatically swept an rf solenoid's frequency through an rf-induced spin resonance and observed its effect on the deuterons' vector and tensor polarizations. After optimizing the resonance crossing rate and maximizing the solenoid's voltage, we measured a vector spin-flip efficiency of 94.2%+/-0.3%. We also found striking behavior of the spin-1 tensor polarization.

Observation of the charge symmetry breaking d+d-->4He+pi(0) reaction near threshold.

We report the first observation of the charge symmetry breaking d+d-->4He+pi(0) reaction near threshold. Measurements using a magnetic channel (gated by two photons) of the 4He scattering angle and momentum (from time of flight) permitted reconstruction of the pi(0) "missing mass," the quantity used to separate 4He+pi(0) events from the continuum of double radiative capture 4He+gamma+gamma events. We measured total cross sections for neutral pion production of 12.7+/-2.2 pb at 228.5 MeV and 15.1+/-3.1 pb at 231.8 MeV. The uncertainty is dominated by statistical errors. These cross sections arise fundamentally from the down-up quark mass difference and quark electromagnetic effects that contribute in part through meson mixing (e.g., pi(0)-eta) mechanisms.

Analysis of the cyclotron facility calibration and aircraft dosimetry results from the liulin-3M instrument

The LIULIN-3M instrument is a further development of the LIULIN dosimeter-radiometer, used on the MIR space station during the 1988–1994 time period. The LIULIN-3M is designed for continuous monitoring of the radiation environment during the BION-12 satellite flight in 1999. A semiconductor detector with 1 mm thickness and 1 cm2 area is contained in the instrument. Pulse high analysis technique is used to determine the energy losses in the detector. The final data from the instrument are the flux and the dose rate for the exposure time and 256 channels of absorbed dose spectra based on the assumption that the particle flux is normal to the detector. The LIULIN-3M instrument was calibrated by proton fluxes with different energies at the Indiana University Cyclotron Facility in June 1997 and had been used for radiation measurements during commercial aircraft flights. The calibration procedure and some flight results are presented in this paper.