Showing papers in "IEEE Transactions on Nuclear Science in 1973"

Review of Sub-Nanosecond Time-Interval Measurements

Abstract: A review of time-interval measurements in the sub-nanosecond regime is presented and the various methods are compared as to their precision, stability, resolution, and other essential parameters. Calibration methods, stabilization, and correction for time walk are also discussed.

A Longitudinal Stability Criterion for Bunched Beams

Abstract: The unstable motion of a bunched beam consists of rigid-bunch (dipole) and higher bunch-shape oscillations of the individual bunches (individual-bunch modes), plus perhaps coupled motion of the different bunches (coupled-bunch modes). Stability is achieved either by decoupling the bunches or by a spread in synchrotron frequencies within a bunch. A stability criterion analogous to the Keil-Schnell criterion for coasting beams is given which includes the effect of a beam interacting with perfectly conducting walls, resistive walls, and resonant structures. Some examples for the CERN accelerators are included.

Parametrization of Linear Coupled Motion in Periodic Systems

Abstract: The Courant-Snyder parametrization for one-dimensional linear motion in periodic systems is generalized to two-dimensional coupled linear motions. The 10-parameter 4×4 symplectic transfer matrix across a period is expressed in two normal-mode invariant phase-advances, four normal-mode periodic "amplitude" functions, and four periodic functions which reflect the strength and structure of the coupling. These parametric functions are also given by differential equations containing the periodic force coefficients appearing in the Hamiltonian. Two bilinear invariants can be constructed. With given horizontal and vertical aperture limitations, these invariants give the four-dimensional phase-space acceptance volume and the propagation of the horizontal and vertical emittances of the beam.

Ion-Implantation Effects in Noncrystalline SiO2

Abstract: Impurity ions (H+, He+, B+, O+, A+, Kr+, and Xe+) have been implanted in high-purity vitreous silica and their production of and interaction with implantation damage was studied by optical absorption techniques. An absorption band at 245 nm (B2-band) is produced by all ions except H+. The implantation of H+ greatly reduces the B2-band absorption intensity produced either by prior or subsequent sample implantation with heavier ions. For ions other than H+, the intensity of the B2-absorption increases with increasing ion mass for a given ion fluence and suggests that the defect giving rise to this absorption is generated by ion energy going into displacement processes. The spectral position of the implantation-induced B2-band is identical with that of a band found in impure as-manufactured fused silica. The band in impure silica is believed to be due to a center consisting of a trivalunt metallic impurity (e.g., Al3+) substituting for Si4+ and an adjacent oxygen vacancy. The results of the present investigation suggest that the implantation induced defect producing the B2 band in high-purity silica is an oxygen vacancy at which the binding electrons of the two adjacent Si atoms can be trapped. If the B2-band is also associated with SiO2/Si interface states in MOS devices as has been suggested, the present results may offer a possibility for reducing the density of these states by H+-implantation.

Latch-Up in CMOS Integrated Circuits

Abstract: The parasitic transistors and pnpn paths present on junction-isolated CMOS circuits have been identified and studied quantitatively. Active SCR structures exist which can be triggered electrically or by a radiation pulse. Detailed studies of SCR paths have been performed on two circuits, the CD4007A and the CD4041A, to relate geometrical and materials parameters to latch-up sensitivity. Both normal bias conditions and bias optimum for obtaining SCR action are employed. Several techniques are proposed to eliminate radiation-induced latchup in future CMOS designs.

Evaluation of Synchrotron Radiation Integrals

Abstract: Many of the important properties of the stored beam in an electron storage ring are determined by integrals, ’ taken around the whole ring, of various characteristic functions of the guide fielci. Some of the integrals are handled easily, but a few are usually estimated graphically - particularly for alternating-gradient guide fields. This report describes a convenient method for evaluating numerically these recalcitrant integrals. In the usual linear approximation, the integrals we wish to consider are most conveniently expressed in terms of four (somewhat redundant) functions of the azimuthal coordinates: p(s) the radius of curvature of the design orbit, n the field index, F(s) the radial betatro; function andT(s) the off-energy (or “dispersion”) function. The Integrals We restrict our attention to guide fields made up of a number of magnetic segments - magnets or straight sections The functions p and n are assumed to have constant values within a given magnet, but vary abruptly at the entrance and erit boundaries. The integrals of interest are given by:

Use of USSR Proton Accelerators for Medical Purposes

Abstract: Proton beams of the Joint Institute for Nuclear Research (LNP, JINR) Dubna synchrocyclotron and of the proton synchrotron of the Institute for Theoretical and Experimental Physics (ITEP) Moscow have been used for medical and biological purposes since 1967. 58 patients in JINR and 163 in ITEP with various types of malignant tumors have been treated. Results of clinical research showed that use of high energy protons for treatment of malignant tumors is quite expedient and may serve as a good approach developing better means for irradiation in oncological therapy. Proposals for proton and meson beams at the JINR high intensity phasotron and for proton beams at the ITEP medical and biological center are discussed. The ITEP center will consist of 4 cabins for therapy and 2 cabins for radiobiological research, which will permit to treat ~ 100 patients per day.

Cyclotron Internal Ion Source with DC Extraction

Abstract: This paper describes a method for increasing the intensities for heavy ion beams accelerated in isochronous cyclotrons at high harmonics (h?5) of the orbit frequency. Normally, only small intensities are obtained at high harmonics because of the low effective accelerating voltage between the ion source and the puller electrode. We have developed and tested a dc ion extraction system for the Oak Ridge Isochronous Cyclotron (ORIC). Use of the dc extraction system has increased beams of 4OAr3+ on the 5th harmonic and 2ONel+ on the 7th harmonic from nanoamperes to microamperes.

A Free Electron Laser

Abstract: This paper includes a brief review of the theory of stimulated bremsstrahlung by relativistic electrons in a periodic magnetic field, a discussion of the possibilities for a classical interpretation, and a description of the apparatus under construction in W. W. Hansen Laboratories of Physics.

Precision Measurements of the Ionization Energy and Its Temperature Variation in High Purity Silicon Radiation Detectors

Abstract: High precision absolute measurements of the ionization energy (?) for alpha particles and electrons have been made in two thick high purity silicon guard ring detectors between 100 K and 250 K. At a fixed energy (E) both ?? and ?e- were found to vary linearly (r = 0.999) with the band gap (WG). ?? and ?e- also increased with E and ?e- ? ??. The slope (??a/?WG) = 1.83 ± 0.04 is the lowest so far reported and is in closer agreement with Drummond and Moll's theoretical value of 1.73. However (?e-/?WG) = 2.87 ± 0.07 is significantly higher. The measured values of ? in electron volts per hole pair (eV/ehp) are: Ee- = 975.2 keV E? = 5483 Kev ?e- (300 K) = 3.631 ?? (300 K) = 3.625 ?e-(100 K) = 3.745 ?? (100 K) = 3.698 The estimated probable error is ± 0.0025 eV/ehp. The ?? values are close to other recent published results. These results taken in conjunction with earlier reported work on Si, Ge, GaAs and CdTe suggest that (??/?WG)? 1.8 in all these semiconductors, i.e. over the WG range from 0.7 to 1.6 eV. Therefore there is a need for further ? measurements on high purity samples of all four materials.

Gamma Ray Efficiency Comparisons for Si(Li), Ge, CdTe and HgI2 Detectors

Abstract: Gamma-ray efficiency measurements were made for Si(Li), Ge, CdTe and HgI2 spectrometers and detectors of comparable sizes for gamma ray energies from 60 keV to 3.85 MeV. Full energy efficiency measurements of cooled Si(Li) and Ge spectrometers and a room temperature CdTe spectrometer show that the efficiencies improve in going from silicon (Z= 14) to germanium (Z= 32) to cadmium telluride (Z= 50) in agreement with the photoelectric cross-sections which vary as Z5. Because of its shorter carrier drift lengths, the CdTe spectrometer must be operated at the highest practical voltages. The detection efficiencies, based on all pulses above a threshold set by noise, were measured for Si(Li), CdTe and HgI2 detectors at room temperature. A 30 keV threshold and small photoelectric cross-section combine to give an efficiency minimum for the Si(Li) detector for 100 keV < E? < 200 keV. Both CdTe and HgI2 detectors iave no such minimum. In addition the higher electronic stopping powers of HgI2 and CdTe in comparison with Si reduce edge effects - an important factor in high energy ?-ray efficiency.

Collective Acceleration of Intense Ion Beams in Vacuum

Abstract: We have developed a diode system with an insulated anode and rear target that operates in vacuum and produces 4 × 1010 neutrons per pulse. The system forms a pinch discharge that ejects a cluster of collectively accelerated ions that attain full energy in 7 cm. Target neutron data and activation analysis with multiple foils show that pulses of 1014 protons with energy up to 15 MeV have been achieved. Experiments with electrode materials and diode geometry have lead to large improvements in focusing and ion beams have been propagated 8 ft in vacuum. The presence of high-energy carbon ions indicates that the pinch has the capability of forming and accelerating multiple ionized high-Z ions.

The Fast Shaving Ejection for Beam Transfer from the CPS to the CERN 300 GeV Machine

Abstract: A fast shaving ejection during 10 or 11 turns is the most promising system for the transfer of the CPS beam to the 300 GeV machine under construction for which the CPS is to be the injector The scheme uses a pair of fast kickers which shift the beam in 10 or 11 steps across an electrostatic septum, located at a position where the amplitude function is increased to near 100m and the momentum compaction function reduced to near zero A prototype system has been installed in the CPS and tests have been carried out at 10 GeV/c with bunched and adiabatically debunched beams The stability of the operation, ejection efficiency, emittance and momentum spread of the ejected beam are of major interest and have been measured The test results are in agreement with theory and no serious difficulties have been observed

The Hydra Electron Beam Generator

Abstract: The Hydra electron beam generator was designed to simrultaneously produce two 1 MV, 0.5 MA, 80 nanosecond electron beams that could be combined to form a single beam. The machine, undergoing final developmental tests, has generated a 0.5 MA, 1 MV peak electron beam from each line. This accelerator consists of a low-inductance Marx generator, two water-dielectric pulse-forming (PF) and impedance-transforming transmission lines and two low-inductance, high-current diodes. A description of the generator is presented along with developmental studies and initial testing data. The Hydra machine is based on accelerator principles described in the literature. The Marx generator is submerged in transformer oil and separated from the transmission line water by a lucite interface. The Marx charges each coaxial PF transmission line which is deionized water insulated to 3 MV in 0.9 microseconds. At peak voltage, a 3 MV SF6 spark gap electrically connects the 4 ohm PF line to the impedance transforming (4 ohm to 2 ohm) transmission line. The pulse is transmitted through this line to the single radial insulator diode. A 30 kilojoule, 100 nanosecond duration electron beam is formed by a cold cathode in each diode.

Room Temperature Annealing of Ionizatton-Induced Damage in CMOS Circuits

Abstract: The effects of ionization on MOS devices as a function of time after exposure to a radiation source are functions of the radiation source and device bias time profiles. This paper presents a discussion, supported by a comprehensive series of experiments, of the time dependence of ionization-induced damage to complementary metal oxide semiconductor (CMOS) devices. Two distinct annealing or recovery mechanisms were investigated: (1) room temperature annealing in the absence of radiation, and (2) radiation enhanced room temperature annealing. Experiments were performed using both electron aid ?-ray sources with ionization rates ranging from 103 rads(Si)/sec to greater than 1011 rads(Si)/sec and observation times extending from 1 msec to 105 seconds. The experiments demonstrate that ionization-induced damage to positively biased MOS devices, such as the n-channel devices in CMOS circuits, can be annealed appreciably at room temperature by additional irradiation of the device with zero gate bias. Thus, when operation of CMOS circuitry during or immediately following radiation exposure is of interest, the experimental semipermanent-type radiation damage data typically reported must be carefully evaluated.

Transient Change in Q and Frequency of At-Cut Quartz Resonators Following Exposure to Pulse X-Rays

Abstract: Study of the transient behavior of AT-cut quartz resonators following pulse irradiation has been extended. In addition to 125 MHz 5th overtone crystal units previously reported, both 32 MHz and 5 MHz 5th overtone units have been studied using several different oscillator circuits, one of which is designed to give the transient resistance at series resonance, RS, as well as frequency as a function of time after pulse exposure. RS is proportional to the acoustic loss, i.e., Q-1, of the resonator. With but one notable exception, the annealing kinetics of the transient frequency offset following pulse irradiation obeys a t-? relationship over three to four decades in time, indicative of a 1D diffusion limited trapping of uncorrelated mobile cation impurities in the crystal lattice. The most significant observations of the post-irradiation behavior of RS is the relatively large RS increase in natural quartz resonators. The transient increase anneals asymptotically to a relatively stable RS value which is somewhat higher than the pre-irradiation RS. The transient and steady-state post-irradiation change in RS is frequency dependent and, based upon the underlying model, should also be temperature dependent. The increase of RS in 5 MHz natural quartz resonators exposed to 104 Rad from the Sandia Laboratories' Hermes II facility is 30 times its pre-irradiation value at 0.2 sec after burst. However, RS for 32 MHz crystal units at .2 sec after exposure to 4 × 104 Rad typically increases only a factor of 2 times the pre-irradiation value.

A Monte-Carlo Calculation of the Neutron Sensitivity of Self-Powered Detectors

Abstract: Self-powered (s-p) detectors are useful for incore neutron measurements in nuclear reactors because of their small size, ruggedness and simplicity. In one type of detector, a delayed current results from the beta activity induced in the device by the neutron flux while a second type gives an instantaneous response due to the compton electrons produced by the gammas released following the capture of neutrons in the device. To test these physical models and more importantly, to point the way to improvements in design without having to resort to excessive experimentation, a Monte-Carlo model was constructed to allow computations to be made of the response of both types of detector. The calculations were performed for Rh and V delayed and Co instantaneous detectors with emitter diameters of .051 cm and insulator thickness of .025 cm in all cases. The agreement with experiment was fairly good and the small discrepancies which occur are discussed in the paper.

The Bevalac -- An Economical Facility for Very Energetic Heavy Particle Research

Abstract: An economical means for the production of high energy, high intensity beams of a variety of heavy-ions is to utilize the existing LBL SuperHilac as an injector for the existing LBL Bevatron. Particle energies from 0.25 to 2.6 GeV/nucleon will be realized. The description of this facility, which will be in operation in late 1973, includes the general arrangements, the modest changes to each accelerator, beam transport line design, and a new bio-medical experimental area.

Dead Layers in Charged-Particle Detectors

Abstract: This paper presents the results of dead-layer thickness measurements on silicon surface-barrier and ion-implanted detectors and a comparison of various methods for measuring dead-layer thicknesses. Our experimental arrangement and estimates of experimental error are discussed. Data on dead-layer thicknesses of n-type and p-type surface-barrier detectors and boron-implanted position-sensitive detectors are given. A linear relation was observed between the dead-layer thickness and the metal electrode thickness for both the rectifying and ohmic contact of barrier detectors. The thinnest dead layers measured were 270A (silicon equivalent) for 15 ?g/cm2 of gold and 460A (silicon equivalent) for 6 ?g/cm2 of aluminum.

Detection of Optical Transition Radiation and Its Application to Beam Diagnostics

Abstract: Optical transition radiation produced by 40-60 MeV electrons crossing thin metallic foils has been studied in order to provide a beam diagnostic device. The radiation yield is roughly one photon per 100 electrons and the intensity appears to be Z independent ; the influence of bremsstrahlung is then fairly weak. Measurements of angular and ? dependence, spectral density and polarisation have been carried out and results are in good agreement with theories. When multiple scattering angles are negligible (< ?-1), a strong eneray dependence, close to ?3 , of the light intensity radiated into small solid angles is found. Moreover, the radiation is peaked in a direction making an angle ?-1 with the beam axis. Suitable optical arrangement make it possible beam position and profile determination. Measurement of the polarisation plane rotation by means of a scanning mirror provides a method of determining the incident angle of the beam onto the target. This device looks promising for diagnostics on particle beams-electrons as well as protons-with normalized energies ? in the range 1-103.

Transient Photocurrents in SOS Structures

Abstract: Silicon-on-Sapphire (SOS) construction reduces junction photocurrents to such low levels that other radiation-induced currents tend to dominate the response of an SOS circuit to transient ionizing radiation The results of experiments and calculations suggest that photoconduction of the sapphire substrate accounts for most of the observed "excess" currents internal to these circuits - while gas ionization effects are significant at the external device terminals

Analytical Prediction of Photo-Compton Emission Currents

Abstract: An analytical procedure for describing vacuum photoemission from one dimensional materials more than one electron range thick has been developed The magnitude, angular and energy distributions are expressed in terms of bulk Photo-Compton current information by algebraic formulae A semi-empirical equation for the low energy component (<100 eV) is also presented Comparison with experimental data is good, comparable to that obtained using more sophisticated Monte Carlo codes, except in extreme cases

Results of Scattering in Radioisotope Imaging

Abstract: It has long been recognized that in-patient scattering can lead to significant ima, ge degradation in nearly all radioisotope imaging. Using biased Monte Carlo codes and experimental determinations, we have undertaken a study of three aspects of this problem: 1. Scattering and attenuation within the patient, 2. Selective rejection of scattered radiation by angular selection of the collimation system, 3. Selective rejection of scattered radiation by energy selection. The model we have assumed consists of point gamma ray sources of energy between 140 and 511 keV, located at depths between zero and 10 cm below the surface of a semi-infinite water medium. Ellett has shown that at the energies of interest here, water is a good representation of a tissue medium. A wide variety of general data on the energy and spatial distributions of the escaping scattered radiation have been catalogued.

Radiation Failure Modes in CMOS Integrated Circuits

Abstract: The radiation sensitivity of commercial and laboratory CMOS processes has been investigated. Failure levels for CMOS circuits have been related to transistor threshold voltage shifts and typical inverter failure modes. CMOS inverter characteristics have been measured as a function of the ionizing radiation exposure for devices fabricated by 10 different manufacturers and representing a total of 15 different processes. By selecting certain processes, CMOS circuits can be obtained which will operate after exposure to an ionizing radiation dose greater than 106 rads (Si).

Beam Induced Gas Desorption in the CERN Intersecting Storage Rings

Abstract: The maximum beam intensity achieved in the ISR has been limited up to now by the beam induced pressure rise which builds up with the stacked proton current. This pressure increase can be explained by ion induced gas desorption from the vacuum chamber. The pressure P, as a function of the stacked proton current I, can be described in good approximation by P = Po/[1-(k?/S)I], where Po is the pressure without beam, S the pumping speed, ? the net gas desorption coefficient in molecules per incident gas ion and ? is a constant. This concept shows the existence of a critical current at which the pressure goes to infinity. The desorption coefficient depends on the primary ion energy, the type of ions and above all, on the surface conditions. Surface treatments yielding low and even negative values of ? are discussed together with experimental results obtained.

Further Studies of Collective Acceleration of Positive Particles Using Intense Electron Beams

Abstract: FURTHER STUDIES OF COLLECTIVE ACCELERATION OF POSITIVE PARTICLES USING INTENSE ELECTRON BEAMS B. Ecker and S. Putnam Physics International Company, San Leandro, CA., 94577 and D. Drickey, Department of Physics, UCLA Protons at 12 MeV and nitrogen nuclei (Nf7) at 29 MeV were produced during propaga- tion of a pulsed 100 kA, 1 MV electron beam (peak values) through initially neutral hydro- gen and nitrogen, respectively. Applied longi- tudinal magnetic fields of 250 gauss or more severely suppressed proton acceleration: 100 gauss had no effect. Protons having at least 3 MeV were observed 11 cm from the plane of injection of the electron beam into the gas- filled acceleration region. At the time of acceleration, the electron beam current front had already propagated substantially beyond the acceleration region. Use of a colder beam than in a previous study1 resulted in increa- sed particle energy and in greater sensitivity of proton energy to hydrogen density. The localized pinch model is strongly supported by some of the data and is compatible with all results. Introduction The first observation of ions accelera- ted by intense electron beams propagating thrcugh initially neutral gas was in 1970 by Graybill and Uglurn.z Since then a number of experimental studies have been reported,lr3'6 gya;;e;;$p;; yF3 Is have been put forth to have been presenied. 133!3 three review papers The present study was a small program that aimed at bringing us closer to a definite conclusion about the na- ture of the acceleration process and its cut- off mechanisms. To this end we have investi- gated mainly the effects of electron beam temperature and of an applied longitudinal magnetic field, and the spatial and temporal relationship between the electron beam and the accelerated ion bunch. As pointed out by Yonas,l5 of the four theoretical models thus

A Platinum In-Core Flux Detector

Abstract: The use of platinum as the emitter in a self-powered flux detector produces a mixed neutron and gamma sensitivity, but typically a higher proportion of prompt response, that is maintained throughout life, than for earlier types. The detector has high output and a low burnup rate, confirmed by two years of extensive tests at high flux.

A High Resolution Position Sensitive Detector for Ultraviolet and X-Ray Photons

Abstract: A new type of position sensitive detection system for ultraviolet and x-ray photons and for particles is described. A compact laboratory model with one-dimensional readout was constructed and tested. The full width at half maximum response to single x-rays was typically 0.13 mm, but the position determination accuracy was comparable to the channel center-to-center spacing of 0.053 mm. The detection system can be readily adapted to two-dimensional readout. Potential applications of this device for single-photon and flux counting in ultraviolet and x-ray astronomy are discussed.