Search

We present a study of an innovative scheme to generate high repetition rate (MHz-class) GeV electron beams by adopting a two-pass two-way acceleration in a super-conducting Linac operated in Continuous Wave (CW) mode. The beam is accelerated twice in the Linac by being re-injected, after the first pass, in opposite direction of propagation. The task of recirculating the electron beam is performed by an arc compressor composed by 14 Double Bend Achromat (DBA). In this paper, we study the main issues of the two-fold acceleration scheme, the electron beam quality parameters preservation (emittance, energy spread), together with the bunch compression performance of the arc compressor, aiming to operate an X-ray Free Electron Laser. The requested power to supply the cryogenic plant and the RF sources is also significantly reduced w.r.t a conventional one-pass SC Linac for the same final energy.

We present here preliminary tests of Medisoft 4, a software procedure for the control and the readout of the single photon counting radiation imaging systems based on the Medipix2 chip (256/spl times/256 pixels, 55 /spl mu/m pitch). The system has been developed in the framework of the Medipix2 collaboration. This hardware and software system is the successor of the system based on the Medipix1 photon counting chip (64/spl times/64 pixels, 170 /spl mu/m pitch). Following the Medipix system evolution, Medisoft 4 allows the user to access the new implemented features such as the higher resolution, the faster data communication rates, the daisy-chain multichip mode, the energy windowed acquisition, the continuous acquisition mode, the double signal polarity (holes and electrons), etc. The readout of the data from the Medipix2 chip is presently via the chip serial bus through a MUROS2 interface board and a commercial input/output board, but a parallel readout via a is also foreseen. The current version (Medisoft 4.0), here the subject of preliminary tests connected via MUROS2 to a Medipix2 chip not bump-bonded to any detector , reads out only single chips and features a reduced set of functionalities. Future versions will read up to eight chips in daisy chain and provide full system performance, including high frame rate acquisitions and spectroscopic imaging. After a description of the Medipix2 chip, its readout interfaces and the Medisoft 4 software architecture, we show the results of preliminary software tests on serial communication protocol and speed with MUROS2 and Medipix2, analogue test input, internal digital analog converters calibration and threshold uniformity.

We present some additional results obtained with the BETAview system, a digital system for real time /spl beta/-imaging based on semiconductor pixel detectors and on a single photon counting read-out chip. We describe the system assembled with a Si detector, 300-/spl mu/m thick, segmented into 64 /spl times/64 square pixels with 170-/spl mu/m pitch. The solid-state pixel array detector is bump-bonded pixel by pixel to a low threshold, single particle counting electronics, the photon counting chip (PCC) developed by the Medipix1 Collaboration for biomedical applications. Each cell (corresponding to a detector pixel) of the front-end chip has a maximum count rate of 2 MHz, a minimum nominal threshold of 1400 e/sup -/ (corresponding about 5 keV in Si), and contains a 15-bit counter. The detector sensitive area is about 1 cm/sup 2/, but several detectors could be assembled in arrays. The measured background counts were about 3.5/spl times/10/sup -2/ cps/cm/sup 2/, which implies a very high sensitivity of the device. The detection threshold used in this experiment was /spl sim/15 keV. We show the results obtained in the real-time monitoring of two biological dynamic processes: an amino acid uptake by living cells and the thermal denaturation process of oligonucleotides. Specifically, we have followed over time the accumulation of a marked amino acid ([/sup 14/C]L-Leucine) into Octopus vulgaris eggs cells. The results, described in Section III-B, show that after about 20 min from the beginning of the uptake process, the radioactively marked eggs become clearly visible over the background culture radioactive medium. In Sections III-C and III-D, we also describe the successful performance of the /spl beta/-imaging system in genetic studies involving the real time reconstruction of denaturation and kinetics curves for two different /sup 32/P-radiolabeled nucleotides.

We have investigated the detection performance of GaAs detectors made with different thickness and contact geometries. A comparison is made between these detection capabilities and the imaging requirements for the following medical applications: digital mammography, digital chest radiography and nuclear medicine. Experimental results and preliminary images are presented and discussed.

We present an autoradiography tool to be used mainly for genetic studies. It performs a quantitative analysis of radioactivity and can follow a dynamic process. We designed several applications, in particular one aimed at detecting hybridization of radio-labeled DNA fragments with known DNA-probes deposited on a micro-array. The technique is based on GaAs pixel array detector and low threshold, large dynamic range and good sensitivity integrated electronics developed for medical applications, suitable to detect markers (gamma or beta) such as 14C, 35S, 33P, 32P, 125I, even at very low activities. A Monte Carlo simulation of β− detection in GaAs is presented here in order to study the spatial resolution characteristics of such a system. For several biological applications, the electronics is required to perform at high temperatures (from 37° to 68°): we present here studies of noise and minimum threshold as a function of the temperature.

A GaAs pixel detector designed for digital mammography, equipped with a 36-channel single photon counting discrete read-out electronics, was tested using a test object developed for quality control purposes in mammography. Each pixel was 200×200 μm2 large, and 200 μm deep. The choice of GaAs with respect to silicon (largely used in other applications and with a more established technique) has been made because of the much better detection efficiency at mammographic energies, combined with a very good charge collection efficiency achieved thanks to new ohmic contacts. This GaAs detector is able to perform a measurement of low-contrast details, with minimum contrast lower (nearly a factor two) than that typically achievable with standard mammographic film+screen systems in the same conditions of clinical routine. This should allow for an earlier diagnosis of breast tumour masses. Due to these encouraging results, the next step in the evolution of our imaging system based on GaAs detectors has been the development of a VLSI front-end prototype chip (MEDIPIX ) in order to cover a much larger diagnostic area. The chip reads 64×64 channels in single photon counting mode, each one 170 μm wide. Each channel contains also a test input where a signal can be simulated, injecting a known charge through a 16 f F capacitor. Fake signals have been injected via the test input measuring and equalizing minimum thresholds for all the channels. On an average, in most of the performing chips available up to now, we have found that it is possible to set a threshold as low as 1800 electrons with an RMS of 150 electrons (10 standard deviations lower than the 20 keV photon signal roughly equivalent to 4500 electrons). The detector, bump-bonded to the chip, will be tested and a ladder of detectors will be prepared to be able to scan large surface objects.

We measured the charge collection efficiency and energy resolution at 60 keV and 122 keV for single-element Cd/sub 0.8/Zn/sub 0.2/Te semiconductor detectors 2/spl times/10/spl times/10 mm/sup 3/, irradiated transverse to the electric field, in view of their possible use for digital radiography. Charge collection efficiency, energy resolution and charge collection time have been measured as a function of the bias voltage. The detector's imaging performance was evaluated, using a scanning procedure, by measurements (at 60 keV) of the line spread function and edge response function of the imaging system; metallic test objects and bone tissue were imaged. Image contrast values as low as C=10% were obtained for a minimum 5:1 S.N.R.

We report here experimental results of the response of two Cd 0.8 Zn 0.2 Te detectors when irradiated with 511 keV photons transverse to the electric field, in view of their possible use for positron emission tomography. Measurements include charge collection time, coincidence resolution time, electron mobility and lifetime, charge collection efficiency, energy resolution and detection efficiency.

A digital autoradiography system based on double sided silicon strip detectors (1.6 × 1.6 mm2 active surface with 100 μm pitch) has been developed and successfully tested with beta-emitting tracers. It is shown here that the system is able to perform imaging of organic material with specific sensitivity as small as 0.002 nCi/mm2, and to record activity measurements with good linearity in the range 0.002–20 nCi/mm2. Autoradiographic images of clusters of mammary cells marked with ortho-(32P)phosphate, obtained with an exposure time of about 10 min are presented.

The use of a double sided mu -strip silicon crystal for X-ray detection is being investigated. The detector is 300 mu m thick and the read-out pitch is 100 mu m for both sides. It operates in capacitance charge division mode by means of floating strips between read-out strips. The detector has been irradiated by /sup 241/Am and /sup 109/Cd sources. Different zones within the 100- mu m read-out pitch have been individually exposed. The following characteristics have been studied as a function of the impact point of the photon: (a) the charge collection mechanism; (b) the relative detection efficiency; (c) the energy resolution; and (d) the spatial resolution. The absolute efficiency of the detector has been measured at three energy values. >

Biological tissues are generally highly scattering samples and the determination of their optical proprierties is difficult to carry out with conventional spectroscopic techniques. Since photoacustic spectroscopy is in fact independent of scattering when it is forward-peaked (as in tissues), we used this techniques to determine the optical absorption coefficient of unprocessed samples of animal tissues (rat skin, bovine liver, muscle, kidney) in the 250-700 nm spectral range.

The study of pulsar bow‐shocks is one of the most promising ways towards the understanding of the interactions between neutron stars relativistic winds and their environment. These objects are best resolved as Hα nebulae but velocity‐driven features are seen also in the radio and X‐ray bands and represent interesting targets for future gamma‐rays telescopes. We present a preliminary multiwavelength catalogue of pulsar bow‐shocks and discuss the prospects for gamma‐rays observations with AGILE and GLAST.

We have developed a technique and a prototype for /spl beta/-rays and /spl gamma/-rays quantitative imaging of biological samples which have been radioactively labeled. The prototype is based on a solid state pixel detector, bump-bonded to a low threshold, single particle counting chip: the detector we used is 200-/spl mu/m thick GaAs, with pixel size 170 /spl mu/m. In this paper we describe an experiment that shows the capability of monitoring a dynamic process. Specifically, [/sup 14/C]L-Leucine uptake by eggs of mollusk cephalopod Octopus vulgaris and the consequent migration of marker into the ooplasm was followed.

The double coincidence probability is a well known limitation to the rate capability of a 2-D detector with independent X- and Y-readout. The authors have implemented a parametric Monte Carlo simulation which could help in optimizing the double coincidence recovery. They have applied the parametric simulation to a specific 2-D solid state detector, they are developing for application in digital mammography.

We present some additional results obtained with the BETAview system, a digital system for real time /spl beta/-imaging based on semiconductor pixel detectors and on a single photon counting read-out chip. In this paper, we describe the system assembled with a Si detector, 300 /spl mu/m thick, segmented into 64/spl times/64 square pixels with 170 /spl mu/m pitch. The solid state pixel array detector is bump-bonded pixel by pixel to a low threshold, single particle counting electronics, the photon counting chip (PCC) developed by the Medipix1Collaboration for biomedical applications. Each cell (corresponding to a detector pixel) of the front-end chip has a maximum count rate of 2 MHz, a minimum nominal threshold of 1400 e~ (corresponding to about 5 keV in Si) and contains a 15-bit counter. The detector sensitive area is about 1 cm/sup 2/, but several detectors could be assembled in arrays. The measured background counts were about 3.5/spl middot/10/sup -2/ cps/cm/sup 2/, which implies a very high sensitivity of the device. The detection threshold used in this experiment was 15 keV. In this paper we show the results obtained in the real time monitoring of two biological dynamic processes: an amino acid uptake and the thermal denaturation process of oligonucleotides. Specifically, we have followed over time the accumulation of a marked amino acid ([/sup 14/C]L-Leucine) into Octopus vulgaris eggs cells. After about 20 min from the beginning of the uptake process, the radioactively marked eggs become clearly visible over the background culture radioactive medium. We also describe the successful performance of the /spl beta/-imaging system in genetic studies involving the real time reconstruction of denaturation and kinetics curves for two different /sup 32/P-radiolabeled nucleotides.

We present an autoradiography system (BETAview) for a quantitative analysis of radioactive markers in biological samples; this system is also able to monitor a dynamic process. It is based on a solid-state pixel array detector, bump bonded to low threshold, integrated electronics developed for medical applications (Medipix). The present assembly is equipped with a 200 μm thick GaAs square detector, about 1 cm side, segmented into 64×64 170-μm size square pixels; simulation and experimental studies show good linearity and high sensitivity to β sources. Imaging tests with β sources of medical and biological interest such as 14C, 35S, 32P are reported.

In the framework of the development of a digital radiography/autoradiography system using solid state detectors, we studied the performance of GaAs pixellated detectors regarding noise level and detection behavior of interpixel space. The detector is a 64×64 pixel array, 200 μm thick GaAs, 150 μm contact size and 20 μm interpixel space. Studies involve I – V curves, detector behavior for long-period biasing, noise as a function of temperature, and possible detection efficiency loss due to interpixel dead spaces.

Thiscollaborationhasalreadyobtainedencouragingresultsabouttheperformanceof200and600mmthicksemi-insulatingGaAsdetectors,intermsofchargecollectionefficiency(c.c.e.),detectionefficiencyandimagingcapabilities,tobeusedassinglephotoncountingdetectorswithphotonsintheradiographicenergyrange.Thepossibleuseofsuchdetectorsinnuclearmedicineimpliesdetectionofmoreenergeticphotons,uptothe140keVofthe 99m Tcsource;thusefficientdetectorsmustbethickerthanthosepreviouslystudied.Inthispaper,wepresenttheresultsoftheinvestigationofelectricalanddetectionproperties(spectra,c.c.e.,energyresolution)ofaseriesofdetectors,whosethicknessrangesfrom 200to1000mm, when irradiated with radioactive sources over the energy range used in nuclear medicine.# 2001 ElsevierScienceB.V.Allrightsreserved. 1. IntroductionIn nuclear medicine, in applications as scinti-graphy and single photon emission computedtomography(SPECT)thephotonstobedetectedare emitted by a radioisotope present into thepatient thanks to a radiopharmaceutical (radio-isotope-taggedcompound),whichcanbeinjected,ingested or breathed [1], in order to ‘‘trace’’variousfunctionsofthebody.Oneoftheprimaryadvantages associated with the use of radionu-clides is the large signal (the emitted radiation)obtainedfromtherelativelysmallmassofradio-nuclide employed for a given study. The minutemass of the radiolabeled material allows for theobservation without disturbance of the systemunder study through pharmacological or toxico-logicaleffect.Thephysicalcharacteristicsofradio-nuclides that are desirable for nuclear medicineimaginginclude:asuitablephysicalhalf-life;decayvia photon emission; associated photon energyhigh enough to penetrate the body tissue withminimal tissue attenuation and low enough toallowingforminimalthicknessofcollimatorsepta;absenceofparticulateemission.

Current pulses produced by absorption of picosecond near-infrared light pulses have been used in order to analyze the shape of the electric field and charge transport properties in semi-insulating (SI) GaAs Schottky barrier X- and gamma-ray detectors. Diodes with square pads of side 0.2–1 mm on 200, 600 and 1000-μm-thick SI GaAs substrates have been illuminated from the front (Schottky) contact, from the back (ohmic) side and laterally between the contacts. Current pulses have been recorded with a fast digital sampling oscilloscope, at room temperature, without using any signal amplification. Current and charge pulse shapes have been analyzed as a function of reverse bias voltage, positioned on the detector surface and optical wavelength around the near-infrared absorption edge of GaAs. The wavelength tuning allows for increasing light penetration lengths. Signal analysis gives the peak current, total collected charge and the charge collection time, which are related to the average strength of the electric field and the drift velocity field, while pulse shape depends on the local value of these fields. The experimental results show that a complete detector characterization is feasible with this optical technique, in a manner analogous to that commonly done with gamma- or X- or alpha-ray sources, with the advantage of analyzing the charge collection time. An additional advantage is represented by focusing the light beam on the detector surface, for 1D or 2D scan.

A system has been developed for the control and readout of an electronic circuit (Medipix) designed for medical X-ray imaging applications. This system (MUROS-1) is based on standard commercial analogue and digital I/O boards and a simple dedicated interface. User-friendly software (Medisoft 3) has been developed to provide full control of the system, including fine tuning of the Medipix circuit, image presentation and post-exposure image processing.

High leakage currents and incomplete charge collection limit the performance of detectors obtained from bulk semi-insulating (SI) GaAs. In this contest, a crucial role is played by the electron limiting contact. We have investigated the effect of an epitaxial p-type layer deposited on the semi-insulating substrate in place of the usual Schottky contact. Electrical characterization evidences an effect of the p-layer only at low voltages, but radiation detection experiments show an improvement of the charge collection efficiency, which is function of the doping level of the p-layer. In particular both /spl alpha/ and X irradiations give evidence of gain mechanisms in the collected charge. From these results, the strong relation between the structure of the electron-blocking interface and the charge collection properties of these detectors comes out.

We made a characterisation of GaAs detectors with an epitaxial p-type layer deposited on the 200 /spl mu/m semi-insulating substrate. The charge collection efficiency for 60-keV photons and 5.49 MeV alpha particle depends on the doping level of the p-layer. When completely depleted (reverse bias >200-300 V), the collected charge can be greater than 100%, implying the presence of some charge gain mechanism. At the same reverse bias and doping concentration, the collected charge depends also on the size of the contact pad. Moreover, the lower the p-doping, the lower the current density. The present findings confirm our previous work, obtaining gains up to 4:1.

We studied pixel radiation detectors for X-ray radiography based on semi-insulating GaAs: in particular, we investigated both annealed and non-annealed contact deposition techniques for the ohmic contact and both ring-guarded and non-guarded Schottky contact, in order to reduce the leakage current and to increase the maximum applied electric field. Spectroscopic characterization with a 60 keV 241 Am source has been performed. Among these different detectors, the CCE can reach 99±6%, while the energy resolution Δ E / E can go down to 4.1±0.2%.

GaAs optoelectronic switches as local control of the HV MSGCs strips are being developed for the CMS experiment. The radiation environment inside the CMS tracker will be very high. Typical hadron fluence will be up to +1014 cm~2 and ionising doses as large as 100 kGy during the experiment lifetime. The aim of this work is to test the performance of some GaAs devices in terms of radiation hardness up to the levels of hadron fluence and ionising doses expected inside the CMS tracker. ( 1999 Elsevier Science B.V. All rights reserved.

A 4096 pixel Photon Counting Chip (PCC) has been developed and tested. It is aimed primarily at medical imaging although it can be used for other applications involving particle counting. The readout chip consists of a matrix of 64 by 64 identical square pixels, whose side measures 170 micrometers and is bump-bonded to a similar matrix of GaAs or Si pixel diodes covering a sensitive area of 1.18 cm2. The electronics in each cell comprises a preamplifier, a discriminator with variable threshold and a 3-bit threshold tune as well as a 15-bit counter. Each pixel can be individually addressed for electrical test or masked during acquisition. A shutter allows for switching between the counting and readout modes and the use of static logic in the counter enables long data taking periods. Electrical test of the chip have shown a maximum counting and readout modes and the use of static logic in the counter enables long data taking periods. Electrical test of the chip have shown a maximum counting rate of up to 2 MHz in each pixel. The minimum reachable threshold is 1400 e with a variation of 350 e rms that can be reduced to 80 e rms after tuning with the 3-bit adjustment. Electrical noise at the input is 170 e rms. Several read-out chips have been bump bonded to 200 micrometers thick GaAs pixel detectors. Test with (gamma) -ray and (beta) sources have been carried out. A number of objects have been imaged and a 260 micrometers thick aluminum foil which represents a contrast to the surrounding air of only 1.9 percent has been correctly imaged.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper we present the results of an experimental study concerning different contact deposition processes on Semi-Insulating (S.I.) GaAs detectors aiming to study and optimize their performance in terms of leakage current, break-down voltage, charge collection efficiency and energy resolution when irradiated with 60 KeV photons; in particular the effect of the mesa etching treatment on the Schottky barrier side of the detectors has been studied. Such treatment certainly improves the detector performances related to the very important issue of the electric field uniformity. Detectors with satisfactory features in view of their possible application to Digital Radiography have been obtained.

Solid state detectors made of Si (4.8/spl times/8 mm/sup 2/) and GaAs (6.4/spl times/8 mm/sup 2/) pixel matrices bump-bonded to the Omega2 and Omega3 electronic read-out systems, developed at CERN for H.E.P. experiments, have been used to obtain autoradiographic images of clusters of human epithelial cells and DNA fragments separated via electrophoresis, both labeled with /sup 32/P. The system has shown a good minimum detectable activity per unit area of 2.10/sup -4/ cps mm/sup -2/, and has proved linear for a count rate in the range 0.2-20 cpa, typical of autoradiography. The pixel dimensions are 75/spl times/500 /spl mu/m/sup 2/ (Si-Omega2) and 50/spl times/500 /spl mu/m/sup 2/ (GaAs-Omega3), respectively. We are able to clearly localize clusters of cells which have incorporated the radioactive tracer and DNA fragments on an electrophoretic gel on paper (blots).

Gallium arsenide pixel detectors processed on a 200 mu m Semi-Insulating (SI) Hitachi substrate were bump-bended to the Omega3 electronics developed at CERN for high energy physics [1]. The pixel dimensions are 50 mu m x 500 mu m for a total of 2048 cells and an active area of similar to 0.5 cm(2). Our aim is to use this system for medical imaging. We report the results obtained after irradiation of the detector with different X-ray sources on phantoms with different contrasts. The system showed good sensitivity to X-rays from Am-241 (60 keV) and Cd-109 (22.1 keV). It is also sensitive to p-particles from Sr-90 as well as from P-32 which is used as a tracer for autoradiography applications. The inherent high absorption efficiency of GaAs associated with the self-triggering capabilities of the pixel readout system reduced considerably the acquisition time compared with traditional systems based on silicon or emulsions. The present configuration is not optimised for X-ray imaging. The reduction of the pixel dimensions to 200 mu m x 200 mu m together with the integration of a counter in the pixel electronics would make the detector competitive for applications like mammography or dental radiology. For certain applications in biochemistry, such as DNA sequencing, where good spatial resolution is required only in one direction, the present setup should allow the best spatial resolution available up to now with respect to other digital autoradiographic systems. DNA sequencing tests are now under way.

We describe a VLSI-based processing system performing X - Y coincidence at a very high rate in the synchronous mode. The processor has been designed for applications in digital mammography with two-sided μ-strip silicon detectors but can be used to provide the computational section of any imaging system that needs fast coincidence. The VLSI chip has been successfully tested on a 32 + 32 channels DAQ chain.

The authors have developed a TDC+Transputer-based acquisition system to study the X-ray imaging capabilities of a silicon /spl mu/-strip detector with 100 and 200 /spl mu/m read-out pitch. This system allows real-time image acquisition and display. The authors present images obtained with an X-ray mammography tube using sub-millimeter high contrast test objects on a 16*16 channels prototype. >

In a previous paper (SPIE Conf. 1584, 1991, 304-307) we proposed an optical fiber interferometric sensor for X-ray dosimetry. Basically, on absorption of a modulated X-ray beam, a temperature rise is produced in a silica fiber, which is detected with a Mach-Zehnder interferometric scheme. In this paper we report on the test measurements performed with our prototype detector using a X-ray rube. A possible application for X-ray synchrotron radiation monitor is discussed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The authors believe that a dedicated parallel computer system can represent an effective and flexible approach to the problem of list mode acquisition and reconstruction of digital radiographic images obtained with a double-sided silicon microstrip detector. They present a transputer-based implementation of a parallel system for data acquisition and image reconstruction from a silicon crystal with 200 mu m read-out pitch. They are currently developing a prototype of the system connected to a detector with a 10 mm/sup 2/ sensitive area. >

In the framework of an experimental study of the possibility of using a double-sided silicon strip detector for digital radiography, and electronic system has been developed to make the signals coming from the two sides of the crystal coincide and hence to define the impact point of X-rays, giving an image matrix as final output. It is based on commercial PALs, and has been built and tested for 32×32 channels. In this configuration the dead time between two subsequent events is ⩽34 ns. Its logic is easily extendable to a large number of channels with a limited increase of the overall dead time and its various stages have been devised in view of a future integration as VLSI

We propose an optical fiber interferometric sensor for x-ray dosimetry. The temperature rise (Delta) T produced in a silica optical fiber irradiated with chopped monochromatic x rays induces a phase shift in the propagation of a He-Ne laser beam with respect to the unirradiated arm of the interferometer. (Delta) T is proportional to the energy released in the fiber. A prototype Mach-Zehnder fiber interferometer has been realized and tested using a laser source to heat the measurement arm; a maximum phase sensitivity of the order of 10-3 radians has been achieved, corresponding to an energy of about 10-5 J absorbed in the irradiated fiber. A possible application is for synchrotron radiation dosimetry.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Semi-insulating gallium arsenide (SI-GaAs) devices have been tested for radiation hardness with 3-4 MeV or 24 GeV proton beams. These devices can be operated in dc mode as optically activated electrical switches up to 1 kV. Both single switches (vertical Schottky diodes) and multiple (8) switches (planar devices) have been studied, by analyzing their current-voltage (I-V) reverse characteristics in the dark and under red light illumination, both before and after irradiation. We propose to use them in the system of high-voltage (-600 V) switches for the microstrip gas chambers for the CMS experiment at CERN. Low energy protons (3-4 MeV) were used in order to produce a surface damage below the Schottky contact: their fluence (up to 2.6/spl times/10/sup 15/ p/cm/sup 2/) gives a high-dose irradiation. The high energy proton irradiation (energy: 24 GeV, fluence: 1.1/spl times/10/sup 14/ p/cm/sup 2/) reproduced a ten years long proton exposure of the devices in CMS experiment conditions. For low energy irradiation, limited changes of the I-V curves in the dark have been observed, with at most a fourfold increase of the leakage current: after exposure, however, the breakdown voltage decreases significantly. For high energy irradiation, we observed-for the vertical Schottky diodes biased at -600 V-an increase of the leakage current and a reduction of the photocurrent after irradiation, with respect to pre-irradiation conditions. Produces up to a 25-times For these diodes, the reduction of the photocurrent/dark current ratio was 25:1. At the same proton energy, an analogous behavior was shown by the planar devices, but after irradiation the current gain may reduce over three orders of magnitude.