Robert Redus

• Principal Investigator at Amptek Inc.

This paper presents the peak-to-background ratio improvement, which can be achieved in PIXE and XRF applications by the use of thin crystal detectors. This improvement becomes apparent in the presence of an intense γ-ray source, which can be produced either after proton irradiation of a sample (PIXE), or after the deexcitation of the radionuclide i...

How should one select the best detector for a particular measurement in energy dispersive X‐ray fluorescence (EDXRF)? How should one select the optimum system configuration, i.e. the best shaping time and beam current? Manufacturers provide a variety of specifications, such as energy resolution and maximum count rate, but these are indirectly relat...

Most energy-dispersive X-ray fluorescence (EDXRF) instruments use Si diodes as X-ray detectors. These provide very high energy resolution, but their sensitivity falls off at energies of 10–20 keV. They are well suited for measuring the K lines of elements with Z < 40, but for heavier elements, one must use K lines at low efficiency or use L or M li...

We have studied timing properties of the Amptek Silcon Drift Detectors (SDD) using pulsed X-ray source designed at NASA Goddard Space Flight Center. The proposed Neutron Star Interior Composition Explorer (NICER) mission will use 56 of these detectors as X-ray sensors in an attached payload to the International Space Station to study time variabili...

Thermoelectrically cooled X-ray detectors are widely used in both portable and laboratory X-ray spectrometers. The most common detectors are fully depleted 500 µm devices behind a Be window to provide a vacuum tight enclosure. These provide good resolution and efficiency for characteristic X-rays from 2 keV to about 20 keV but a larger energy range...

A portable Gamma-Ray Spectroscopy system has been designed and tested for identification of nuclear materials in the field. A P-I-N CdZnTe detector was developed to minimize the leakage current and to improve energy resolution. The detector has a sensitive volume of 200 mm3 and has been constructed with novel heterojunction contacts. Thermoelectric...

Continued improvements in the manufacturing of Cd1−xZnxTe (CZT) material have resulted in a practical thermoelectrically cooled X-ray and gamma-ray detector of very high energy resolution. A high resolution spectroscopy system was used to measure the Fano factor in CZT at temperatures down to -40°C. The best resolution of the 5.9 keV 55Fe peak was...

Portable/hand-held X-ray fluorescence (XRF) instruments now achieve performance comparable to laboratory-sized, expensive, liquid nitrogen cooled systems. The availability of these systems has expanded XRF applications out of the laboratory to in situ analysis including that for lead in paint, alloy identification, process control, restriction of h...

Silicon diodes have traditionally been the detectors of choice for quantitative X-ray spectroscopy. Their response has been very well characterized and existing software algorithms process the spectra for accurate, quantitative analysis. But Si diodes have limited sensitivity at energies above 30 keV, while recent regulations require measurement of...

All X-ray and gamma-ray spectroscopy systems exhibit pulse pile-up and dead time losses arising in the signal processing electronics. To accurately determine the true incoming count rate and spectrum, one must determine and correct for these losses. Many correction methods were developed using analog shaping amplifiers and multichannel analyzers, p...

Since radiation detectors and associated electronics operate on pulses, time domain or transient simulations are used but neglect electronic noise. Traditional noise analysis yields the rms magnitude of noise fluctuations but does not show how noise affects time-variant or nonlinear circuits. These effects are not well described by either noise-fre...

The accuracy and precision of energy dispersive X-ray fluorescence (EDXRF) improve with improved detector energy resolution. However, there are always trade-offs between the highest energy resolution and the highest count rates, there are practical difficulties in achieving the very best energy resolution, and there are many system level issues bey...

The VeriSpreaderTM radiation detection system will monitor every container passing through a shipping terminal without impeding the flow of commerce by making the radiation measurements during normal container handling. This is accomplished by integrating neutron and spectroscopic γ-ray detectors into a container crane spreader bar, the part of the...

Compact, high performance X-ray and gamma-ray spectroscopy systems are required for many applications, both in the field and in the laboratory. The X-123 provides this by combining Amptek's thermoelectrically cooled X-ray and gamma-ray detectors and Amptek's digital signal processing technology with a compact, high efficiency power supply in a smal...

The Low Energy ElectroStatic Analyzer (LEESA) will measure electrons and protons from 100 eV to 50 keV onboard the DSX spacecraft. This sensor uses hemispherical sector ESAs to achieve a single, 50 degree pitch angle bin. LEESA is a new instrument, based on heritage designs of sensors, analog electronics, and power supply electronics. During the fi...

The Medium Energy Particle Sensor (MEPS) to be developed as part of the Space Environment Sensor Suite (SESS) for the NPOESS Spacecraft will cover the energy range from 150keV to 10MeV for protons and 50keV to 4 MeV for electrons. It will also include dosimeter capability similar to that of the AMPTEK Compact Environmental Anomaly SEnsor (CEASE). T...

The Low Energy Particle Sensor (LEPS) to be developed as part of the Space Environment Sensor Suite (SESS) for the NPOESS Spacecraft is a continued enhancement of the SSJ Sensors flown on the Defense Meteorological Satellite Program (DMSP)Spacecraft since 1973. In addition to meeting the operational requirements of the DoD and civilian communities...

This paper describes the development of a field portable gamma-ray spectroscopy system based on multielement CdTe detectors. A stack of multiple planar detector elements is used, with each individual element thin enough for good charge transport but with the outputs summed so that the full volume is used. The detector elements are CdTe diodes mount...

This paper describes the peak-to-background ratio improvement that can be achieved in PIXE and XRF applications by the use of thin crystal detectors. This improvement becomes apparent in the presence of an intense γ-ray source, which can be produced either during proton irradiation of a sample (PIXE) or in the deexcitation of the radionuclide in ra...

Thermoelectrically cooled X-ray detectors based on Si-PIN and Cd_1-xZn_xTe (CZT) devices are now widely used in field-portable X-ray fluorescence (XRF) instrumentation. A previous generation of detectors provided high-energy resolution comparable to that of cryogenic detectors, but at much reduced sensitivity. Recent research at...

A compact particle telescope has been developed to measure highly penetrating protons in space, measuring the differential energy spectrum of protons between 25 and 440 MeV and the integral flux above 440 MeV. This instrument combines new detector materials, an innovative sensor geometry, and a combination of active and passive shielding to obtain...

The Compact Environmental Anomaly Sensor (CEASE) is an instrument designed to provide real-time space environment hazard warnings to the host spacecraft. In this paper, we report on the first year of on-orbit operation of this instrument and describe its performance with particular emphasis on its engineering, hazard-warning function

The solar cycle dependence of dose rates in the low-altitude "horns" of the outer zone electron belt is examined using data from TSX5/CEASE (solar maximum epoch) and APEX/PASP+ (solar minimum epoch). It is found, after normalizing the dose rates to account for the different shielding geometries, that the ratio of PASP to CEASE dose rates is ~4 for...

This document is the Final Report for the Compact Environmental Anomaly Sensor (CEASE) Flight Support Program carried out by Amptek, Inc. under Air Force contract F19628-96-C-0063. The goal of this program was to support the flight code development, functional testing, environmental testing, calibration spacecraft integration, and initial on-orbit...

An improved compact, high-resolution spectroscopy system has been developed in which Si-PIN or Cd1−xZnxTe radiation detectors and certain preamplifier components are mounted on a thermoelectric cooler. This system combines very high-energy resolution with the convenience of room temperature operation, since the cooling is transparent to the user. S...

This report contains the summary of the scientific and engineering work performed as part of the development of the High Energy Proton instrument (HEP) and of the Low Energy Particle and Dosimetry instrument (LEPDOS). These instruments are part of the SOBEDS suite of instruments being developed by Amptek, Inc. The purpose of the HEP instrument is t...

The outer space environment experienced by modern, electronically sophisticated spacecraft can be very hostile due to interactions between complex, sensitive electronics systems and the naturally occurring energetic particle population indiginous to the solar system. The Compact Environmental Anomaly System (CEASE) has been developed as a small, lo...

A compact, high-energy-resolution X-ray and gamma-ray spectroscopy system has been developed using thermoelectrically cooled detectors to combine excellent energy resolution and convenient operation. A Si PIN diode is used for low-energy X rays, while a Cd{sub 1{minus}x}Zn{sub x}Te (CZT) detector is used for higher-energy photons. Cooling is totall...

Anticoincidence detectors are required for a variety of satellite instruments, including high energy gamma-ray telescopes, in order to differentiate ambient background radiation from signals of interest. Presently, most anticoincidence systems use scintillators coupled to photomultiplier tubes. We have demonstrated that it is now possible to use ve...

A wide variety of applications require high resolution, high sensitivity, gamma ray spectrometers which are portable, compact, and rugged enough for field operations. We are developing a laboratory prototype of a semiconductor detector system meeting these requirements. This spectrometer uses multiple CdTe radiation detectors for high counting effi...

Large area silicon avalanche photodiodes have been fabricated with maximum avalanche gains exceeding 10,000 and excellent signal to noise ratios. A model of device performance has been developed in which previously developed general expressions are numerically integrated using actual fabrication parameters. The gain, statistical fluctuations in the...

A combined video and gamma ray imaging system has been developed which can rapidly determine the location, distribution, and intensity of gamma ray sources. This instrument includes both a conventional video camera and a gamma ray imaging system, which is based upon a position sensitive photomultiplier tube, a scintillator, and a pinhole collimator...

To satisfy the needs of high energy gamma ray imagers for industrial nuclear imaging applications, three high energy gamma cameras are presented. The RMD-Pinhole camera uses a lead pinhole collimator and a segmented BGO detector viewed by a 3 inch square Position Sensitive Photomultiplier Tube (PSPMT). This pinhole gamma camera displayed an energy...

Arrays of high speed, high gain avalanche photodiodes (APDs) have been developed for use as high sensitivity optical photon detectors. The 1 mm2 area APD pixels yield a maximum avalanche gain of 40,000 and a high signal-to-noise ratio with only moderate cooling (-22 degrees to -43 degrees C). These devices demonstrate 70% detection efficiency for 6...

An integrated imaging sensor system is being developed to enhance operations of robots and telerobotic systems used in nuclear industry. This system combines a gamma ray image of the distribution of radioactivity with a video image of the area, allowing a rapid and intuitive determination of the source location. The gamma ray imaging system is base...

A prototype portal imager using a linear array of 256 CdTe photovoltaic detectors, each 2 mm×2 mm×2 mm, is constructed. The array is attached to a compact linear scanner which is to be mounted in a cassette shaped package located below the patient table. The array of detectors is moved under the patient during image acquisition. The high stopping p...

The design and operation of the proton telescope (PROTEL) on the Combined Release and Radiation Effects Satellite (CRRES), which operated in a low-inclination, geosynchronous transfer orbit from 25 July 1990 to 12 October 1991, are described. PROTEL makes well-calibrated, high-angular-resolution measurements of the proton differential energy spectr...

Recent advances in photomultiplier tube technology have led to the availability of position sensitive photomultiplier tubes (PSPMTs). These tubes make it possible to build a new generation of imaging instruments for gamma rays and other types of ionizing radiation. We have investigated the use of these tubes for the construction of several prototyp...

Novel radiopharmaceuticals have recently generated a resurgence of interest in the use of hand-held, intraoperative nuclear probes to provide in vivo localization of tumors. A hand-held intraoperative nuclear imaging probe is being developed based on a position-sensitive photomultiplier tube. A compact bench-top prototype system has been built whic...

A novel nuclear survey instrument with an imaging capability is being developed for remotely locating high-level radioactive sources with minimal operator exposure. It combines an image of the distribution of radioactivity with a video image of the area containing the source, allowing rapid, remote location of the source. The nuclear imaging system...