Oak Ridge Isochronous Cyclotron Research Articles

A Broad-Beam Biology Facility for Proton Irradiation at the Oak Ridge Isochronous Cyclotron

The broad-beam facility of the Oak Ridge Isochronous Cyclotron was developed primarly for whole-body irradiation of mice with 60-MeV protons. The proton beam is defocused, with the use of three quadrupole lenses and thin scattering foils, to provide a uniform flux over a rectangular exposure field 10 by 12.5 cm. The beam, after leaving the vacuum system, passes through a thin-walled ionization chamber, and the beam charge is measured with a Faraday cup. Output of the ion chamber operates a current integrator that can be preset to stop irradiation at the desired absorbed dose, calculated from proton fluence and from range-energy tables. The beam profile is routinely surveyed with a pair of remotely controlled thimble chambers providing a readout of both dose rate and integral output. The chambers are positioned at the edges of the field to monitor operation during exposures. Small fluoroglass dosimeters also are used routinely to measure beam uniformity and range. Entrance-to-exit dose variation is minimiz...

An input-capacity-insensitive, charge-sensitive preamplifier for simultaneous use in vacuum with fast amplifiers for charged-particle studies with semiconductor detectors

A low-noise, charge-sensitive preamplifier was designed for service in a system used for experimental studies of charged particles with the Oak Ridge Isochronous Cyclotron 60-MeV proton beam 1). In these studies all charged particles from 1 to 60 MeV produced in targets bombarded by 60-MeV protons were examined and identified by an on-line computer using two methods simultaneously: time-of-flight mass identification, and E by d E/d x mass and charge identification. The first method requires a detector and preamplifier system that can resolve the ∼3-nsec flight-time difference between 10-MeV 3He and alpha particles. The second method requires a system with an energy resolution of 100 keV for 60-MeV protons. The charge-sensitive preamplifier described herein meets these requirements with good versatility and without sacrificing other performance characteristics. The preamplifier consists of a charge-sensitive loop only. Its charge sensitivity is from 54 mV/MeV (in Ge) to as much as 2 V/MeV with from one to three FET's in parallel at the input without the addition of parasitic suppressors. For 1.6-μsec RC- RC pulse shaping, the measured noise of this preamplifier at room temperature is 1.1 keV fwhm (referred to Ge), measured with zero detector capacity but with all other connections made, including a 1-pF test pulse capacity. An input pulse of either polarity is accepted; the maximum output is either ±3.0 V into 93 ω with better than 0.05% linearity. The temperature stability is better than 0.05% from −10° to 50°C, and as measured is determined by the temperature stability of both the charge injection capacitor and the feedback capacitor. The gain stability under prolonged vacuum operation inside a scattering chamber is better than 0.05% for 5 h. To increase the signal received by the fast amplifiers used simultaneously with this charge-sensitive preamplifier and to minimize the loop closure time, no bandwidth suppression is used even for the larger feedback ratios with three FET's. Under these conditions the preamplifier is stable against parasitic oscillations with input cable impedances from 50 to 125 ω, cable lengths continuously variable from 0 to 4 ft, and input capacities at the ends of these cables from zero to several hundred picofarad. One of the necessary design considerations achieved with this preamplifier is that the dc bias conditions are adequate to ensure linear operation over the large dynamic range of energies expected. This includes energy depositions of ∼16 MeV in a 100-μ diode, whose collection time is faster than the response time of the charge-sensitive loop. The design also includes an internal feedback network which when adjusted permits the preamplifier to operate with a detector capacitance from 0 to 100-pF with no detectable change in the output pulse amplitude.

New Erbium Isotope,Er155

A new erbium isotope $^{155}\mathrm{Er}$ was produced by bombarding enriched $^{156}\mathrm{Dy}$ with $\ensuremath{\alpha}$ particles accelerated in the Oak Ridge Isochronous Cyclotron. In the experiments, recoil nuclei ejected from the thin target were collected on beryllium foils. After bombardment, the activity collected on the catchers was assayed with an $\ensuremath{\alpha}$-particle Si(Au) spectrometer. The new isotope was found to have a half-life of 5.3\ifmmode\pm\else\textpm\fi{}0.3 min; its $\ensuremath{\alpha}$-decay energy was measured to be 4.01\ifmmode\pm\else\textpm\fi{}0.03 MeV. The mass assignment of $^{155}\mathrm{Er}$ was established by measuring an excitation function for its production for $\ensuremath{\alpha}$-particle bombarding energies from 59.2 to 72.6 MeV.

Beam loss due to the vr- vz= 1 and 3vr- vz= 3 resonances

In the Oak Ridge Isochronous Cyclotron (ORIC) there had been unexplained beam loss when protons were accelerated to maximum energy. Since recent successes in computing trim-coil currents lend assurance that the magnetic field is reasonably isochronous, the computed orbit properties can now be compared with the observed beam behavior. The orbit properties computed for proton acceleration indicate that the 60-MeV beam passes through the v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> - v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> =l resonance; computed and measured radii for beam loss are in excellent agreement. Computations also show that the beam is passing through, and in some cases closely following, the essential resonance 3v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> - v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> = 3. Under certain operating conditions where it had been very difficult to accelerate the beam to full radius, the valley coils (which can vary the axial focusing strength over a wide range) can now be adjusted so as to avoid the v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> - v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> = 1 coupling resonances and allow acceleration of the beam to full radius without significant beam loss.

Excitation Functions for Radioactive Nuclides Produced by Deuteron-Induced Reactions in Iron

Cross sections were measured for the production of radioactive nuclides by deuteron-induced reactions in natural iron at bombarding energies below 40 MeV. Deuteron beams of the Oak Ridge isochronous cyclotron were used to bombard stacked iron foils. $\ensuremath{\gamma}$ spectra of individual foils were measured with a Ge(Li) spectrometer. Radioactivities with half-lives greater than 20 min were measured. Excitation functions were obtained for $^{55}\mathrm{Co}$, $^{56}\mathrm{Co}$, $^{57}\mathrm{Co}$, $^{58}\mathrm{Co}$, $^{52}\mathrm{Mn}$, $^{54}\mathrm{Mn}$, $^{54}\mathrm{Mn}^{m}$, and $^{51}\mathrm{Cr}$. Cross sections predicted by a compound-nucleus evaporation theory are in reasonable agreement with the experimental results.

Some Biological Effects of Low-Energy Protons on Skin

Rhesus monkeys (Macaca mulatta) were exposed to 28-MeV, 21-MeV, 14-MeV, and 5-MeV protons at the Oak Ridge Isochronous Cyclotron with doses from 500 to 2000 rads. The theoretical depths of penetration of these low-energy protons are 8, 5, 2, and 0.4 mm, respectively. Acute skin damage was assessed. No clinically observable effects resulted from exposure to 5-MeV protons up to 2000 rads. Acute skin effects were noted following exposures to 14-MeV, 21-MeV, and 28-MeV proton irradiation, and these effects were found to be a graded response dependent on both proton energy and dose.

Experimental Study of theT=TzStates inZr90via a (He3,d) Reaction

$^{89}\mathrm{Y}(^{3}\mathrm{He},d)^{90}\mathrm{Zr}$ data taken with the Oak Ridge isochronous cyclotron with ${{E}^{3}}_{\mathrm{He}}=25$ MeV are analyzed. 35 states are observed between 5.08- and 8.12-MeV excitation with ${l}_{p}=2$ and ${l}_{p}=0$. These states are considered to be the antianalog single-particle-hole states of the ${{p}_{\frac{1}{2}}}^{\ensuremath{-}1}{d}_{\frac{5}{2}}$, ${{p}_{\frac{1}{2}}}^{\ensuremath{-}1}{s}_{\frac{1}{2}}$, and ${{p}_{\frac{1}{2}}}^{\ensuremath{-}1}{d}_{\frac{3}{2}}$ proton configuration in $^{90}\mathrm{Zr}$ mixed with states. The possibility exists that there are some additional states of the ${{p}_{\frac{1}{2}}}^{\ensuremath{-}1}{d}_{\frac{3}{2}}$ proton configuration higher than 8.12 MeV. The energy separation between the centroid of each of the ${T}_{l}={T}_{0}\ensuremath{-}\frac{1}{2}$ groups and the corresponding analogs with ${T}_{g}={T}_{0}+\frac{1}{2}$ is found to be approximately 7 MeV. The strength of the isobaric-spin-dependent potential, responsible for the splitting of the ${T}_{l}$ from the ${T}_{g}$ states, is calculated to be 148 MeV. Spectroscopic factors are extracted and are compared with theoretical sums of spectroscopic factors. The total number of ${T}_{l}$ states seen is in good agreement with the number calculated from considerations of core-polarization states mixed with the antianalog states through nuclear interactions.

Be9(p, pα)He5Reaction at 57 MeV

The ${\mathrm{Be}}^{9}(p, p\ensuremath{\alpha}){\mathrm{He}}^{5}$ reaction was studied using 57-MeV protons from the Oak Ridge isochronous cyclotron. The correlated energies of both the emitted protons and $\ensuremath{\alpha}$ particles were measured at detection angles (${\ensuremath{\theta}}_{p}, {\ensuremath{\theta}}_{\ensuremath{\alpha}}$) of (94\ifmmode^\circ\else\textdegree\fi{}, -35.3\ifmmode^\circ\else\textdegree\fi{}), (105\ifmmode^\circ\else\textdegree\fi{}, -30\ifmmode^\circ\else\textdegree\fi{}), and (116\ifmmode^\circ\else\textdegree\fi{}, -25.1\ifmmode^\circ\else\textdegree\fi{}), where the detectors were coplanar with the beam. In addition, an angular correlation was measured by fixing ${\ensuremath{\theta}}_{p}$ at 105\ifmmode^\circ\else\textdegree\fi{} and varying ${\ensuremath{\theta}}_{\ensuremath{\alpha}}$ from -21\ifmmode^\circ\else\textdegree\fi{} to -39\ifmmode^\circ\else\textdegree\fi{} in 3\ifmmode^\circ\else\textdegree\fi{} steps. The data for the reaction leading to the ground state of ${\mathrm{He}}^{5}$ were found to be consistent with quasifree scattering of the incident protons by $S$-state $\ensuremath{\alpha}$-particle clusters in ${\mathrm{Be}}^{9}$. Analysis in terms of a plane-wave impulse approximation yields a momentum density distribution for the struck $\ensuremath{\alpha}$ particles which has a half-width of 0.27 ${\mathrm{F}}^{\ensuremath{-}1}$, and a probability of finding an $\ensuremath{\alpha}$-particle cluster in ${\mathrm{Be}}^{9}$ of ${0.25}_{\ensuremath{-}0.12}^{+0.25}$.

The (d, 3He) reaction on 126Te, 128Te and 130Te nuclei

The (d, 3He) reaction was employed to study the shell-model composition of the ground states of 126Te, 128Te and 130Te. The study was performed with a 34 MeV deuteron beam from the Oak Ridge Isochronous Cyclotron. A silicon counter telescope was used to detect the 3He particles. Angular distributions for the 3He groups were compared with DWBA predictions to obtain angular momentum transfers and spectroscopic factors. States were observed corresponding to the removal of protons from the 1 g 7 2 , 2 d 5 2 , 2 d 3 2 , and 3 s 1 2 shell-model orbits. In additions, states are populated which are due to pick-up of 1 g 9 2 , 2 p 1 2 and 2 p 3 2 protons from the next (lower) shell. The Q-value of the 130Te(d, 3He) 129Sb reaction was measured to be −4.55±0.03 MeV; it significantly increases the accuracy of the measured mass for 129Sb.

New neptinium isotopes, 230Np and 229Np

Two new neptunium isotopes 230Np and 229Np were produced by bombarding enriched 233U with protons at the Oak Ridge Isochronous Cyclotron. In the experiments, recoil nuclei ejected from the target were collected and then assayed with an α-particle spectrometer. The 230Np and 229Np isotopes were found to have respective α-particle energies and half-lives of 6.66±0.02 MeV and 4.6±0.3 min and 6.89±0.02 MeV and 4.0±0.2 min. The 226Pa and 225Pa collateral series from the decay of the neptunium parents were also seen. The α-particle energies found for the 225Pa series are more precise than previously available values: 225Pa, 7.25±0.02 MeV (new value); 221Ac, 7.63±0.02 MeV; 217Fr, 8.31±0.02 MeV.and 213At, 9.06±0.02 MeV. Evidence for the possible decay of 221Ac via emission of a 7.42 MeV α-particle to an excited state of 217Fr is presented. The α-particle energies measured for 230Np, 229Np and 225Pa verify the predictions of Viola and Seaborg from α-decay systematics.

Identification of the T< components for single-proton single-proton hole states in 90Zr

89Y( 3He,d) 90Zr data taken with the Oak Ridge Isochronous Cyclotron at E 3 He = 25 MeV are analyzed. Previously seen states at 0.0, 1.76, 2.32, 2.73 MeV are used for a check on the analysiss. Five l p = 1 states are found in the vicinity of 4.5 MeV excitation, and this is plausible only if the ground state of 89Y is not pure p 1 2 . Fourteen l p = 2 states are found between 5.08 – 6.64 MeV excitation, which are considered to be the T < = T z single particle-hole states of the p case1 2 −1 d 5 2 proton configuration in 90Zr.

A Diagnostic System for Optimization of the External Beam Quality of the Oak Ridge Isochronous Cyclotron

The parameters of the external beam that are of prime importance to the experimenter are the emittance, energy spread, intensity of analyzed beam, and time structure. Diagnostic equipment has been developed for routine measurement and optimization of these parameters.

Whole-Body Irradiation of Primates with Protons of Energies to 400 Mev

The effect of ionizing radiation on man is of vital interest to the space program. To further knowledge of these effects, a study involving whole-body exposures of primates to ionizing radiation has been initiated. The primate Macaca mulatta has been chosen as a suitable subject. Part of the study calls for irradiation of these animals by protons of various energies in the range 32 Mev to 2.3 Bev. This paper outlines the physical aspects and dosimetry of the whole-body irradiations with 32-Mev, 55-Mev, 138-Mev, 250-Mev, and 400-Mev protons, embracing the energy region where meson production can be considered negligible. The resultant biological effects are described elsewhere (1-8). At all energies the primates were placed in rotating cages during exposure to obtain a uniform distribution of dose. In the 32-Mev and 55-Mev exposures the protons did not penetrate completely through the primates, and the surface dose was used as the reference. At the higher energies the protons passed through the primates, and reasonably uniform body doses were obtained. Doses from 25 to 7000 rads were given, the dose rate varying with the different irradiation facilities. The 32-Mev and 55-Mev experiments were performed at the Oak Ridge Isochronous Cyclotron, the 138-Mev experiments at the Harvard University Synchrocyclotron, and the 250-Mev and 400-Mev experiments at the University of Chicago Synchrocyclotron. Dose-rate considerations made it necessary to use the three different facilities. At Harvard and Chicago multiple-Coulomb scattering was used to obtain the broad-beam profile required for the exposures; at Oak Ridge the beam optics system was able to defocus the beam to given an acceptable proton distribution. Exposures at each energy constituted an entity in themselves; however, the procedures followed are similar and are covered in detail only for the 32-Mev exposures. Beam measurements were made to determine the proton flux, and hence the time-

Apparatus for measuring spectra of radioisotopes with half-lives from one second down to a millisecond

An apparatus was built and used satisfactorily to measure the energy spectra and half-lives of short-lived delayed proton and alpha-particle emitters produced in the Oak Ridge isochronous cyclotron. The equipment is easily adjustable to measure half-lives in the range of a msec to one sec. This technique can be used to measure the spectrum of any type of radiation simply by inserting a suitable detector.

Polarized-proton scattering facility at the Oak Ridge isochronous cyclotron

In the facility described, polarized-proton beams are produced either as recoil protons from a hydrogen-gas target bombarded by α-particles or as elastically scattered protons from a solid 40Ca target. At a polarized-proton energy of 40 MeV, the polarization is 89±7% for the hydrogen polarizer and 35.5±3% for the 40Ca polarizer. A system of two quadrupole-doublet lenses transports the polarized proton beam about 18 ft and focuses the beam to a 1 4 ″ by 1″ spot at the center of a scattering chamber. Energy spectra of protons scattered from a secondary target are obtained at 32 angles simultaneously by using 32 NaI scintillation counters connected to the X-ADC of a Victoreen 20 000-channel multiparameter analyzer used as thirty-two 400-channel analyzers.

A Total-Absorption Detector for 60-MeV Protons Using Lithium-Drifted Germanium

A lithium-drifted germanium diode has been used for total-absorption detection of 59-MeV protons from the Oak Ridge Isochronous Cyclotron. The detector is 1.9 cm in diameter, has a depletion depth of 6 mm, is cooled to less than 85° K, and is sealed in an aluminum can with a 0.0026-in.-thick window. The diode was oriented so that the protons entered in a direction parallel to the detector junction. The energy resolution attained for 59-MeV protons was 150 keV (FWHM), uncorrected for energy straggling in windows of 76 keV, for approximately 60 keV of beam resolution, and for electronic noise. The peak-to-total ratio, determined by using an anticoincidence collimator, was as high as 0.94, which is comparable to 0.96 observed elsewhere for NaI. When the collimator was moved along a line parallel to the junction and perpendicular to the beam, the energy resolution and peak-to-total ratios remained constant within the experimental accuracy over a 10-mm scanned distance. As the collimator was moved in a direction perpendicular to the junction and toward the depleted material, the peak-to-total ratio decreased, as was expected from multiple scattering calculations. When the diode was connected by a 125-ohm terminated coaxial cable to a fast amplifier, a rise time of 4-5 nsec was observed. Since the protons entered the detector parallel to the junction, pictures obtained show the superposition of nearly rectangular current pulses arising from hole and electron collection. The length of the pulses is correlated with the point of incidence of the collimated beam.

The Oak Ridge Isochronous Cyclotron; Progress and Status, January 1966

The Oak Ridge Isochronous Cyclotron; Progress and Status, January 1966

Improvements in the Oric RF System

The Oak Ridge Isochronous Cyclotron has been operating since January 1963. Initial experience with the rf system was enlivened by destructive sparking and general instability at the upper end of the rf tuning range. A network of protective devices developed during the past two years almost eliminates spark damage and improves the stability of the system. A multistage rf voltage regulator was also developed and installed.

General Description of the NRL Sector-Focusing Cyclotron Facility

The nuclear physics research facilities at NRL are presently being expanded by the addition of a Sector-Focusing Cyclotron Facility. The Cyclotron is essentially a copy of the Oak Ridge Isochronous Cyclotron and much of the facility concept is patterned after the Oak Ridge Installation. A beam optics system was designed that satisfied the specified criteria as to image quality, and then a building design was coupled to this beam optics system. Included in the facility are a cyclotron and beam preparation vault, and three experimental rooms which are sufficiently well shielded from each other and from the cyclotron vault, so that personnel have access to any two experimental areas while the third is utilizing the cyclotron beam. Eleven separate beam paths will permit set-up of many different experiments simultaneously. The main experimental wing of the building also includes two experimental staging areas, a control room, and a data accumulation room. A laboratory-office wing provides space for check-out of various apparatus, a target preparation room, a machine shop, a darkroom, counting rooms, a library, a conference room, and offices for the staff. The facility will be used to study nuclear interaction mechanisms, polarization phenomena, nuclear structure, heavy ion, and neutron physics, as well as various areas of applied research.

Unique features in the Oak Ridge Isochronous Cyclotron

The results of the initial month of operation of the Oak Ridge Isochronous Cyclotron are presented along with a description of the machine. An 8-MeV proton beam was obtained at the full 32-in. radius on 18 March. Beam-phase studies since that time have lowered the threshold voltage from 13 to 8 kV. ORIC is designed as a variable energy, three-sector, 76-inch, fixed-frequency cyclotron to accelerate protons to 75 MeV and nitrogen 4 + to 100 MeV.