123530909
Intercomparison of the response of dosemeters used in high energy stray radiation fields
The response of dosemeters in three different high energy stray radiation fields at CERN has been investigated. Compared to similar experiments performed in the past, new types of instruments were employed, and spectral information on the neutron field was acquired. The results are discussed in the light of previous experience and present knowledge with respect to the composition of the stray fields
120071736
Radiation hardness of cryogenic silicon detectors
Abstract We shall review test results which show that silicon detectors can withstand at 130 K temperature a fluence of 2×10 15  cm –2 of 1 MeV neutrons, which is about 10 times higher than the fluence tolerated by the best detectors operated close to room temperature. The tests were carried out on simple pad devices and on microstrip detectors of different types. The devices were irradiated at room temperature using reactor neutrons, and in situ at low temperatures using high-energy protons and lead ions. No substantial difference was observed between samples irradiated at low temperature and those irradiated at room temperature, after beneficial annealing. The design of low-mass modules for low-temperature trackers is discussed briefly, together with the cooling circuits for small and large systems.
16425228
Measurement of the pressure dependence of air fluorescence emission induced by electrons
The fluorescence detection of ultra high energy (J10 18 eV) cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules, which are excited by the cosmic ray shower particles along their path in the atmosphere. We have made a precise measurement of the fluorescence light spectrum excited by MeV electrons in dry air. We measured the relative intensities of 34 fluorescence bands in the wavelength range from 284 to 429 nm with a high resolution spectrograph. The pressure dependence of the fluorescence spectrum was also measured from a few hPa up to atmospheric pressure. Relative intensities and collisional quenching reference pressures for bands due to transitions from a common upper level were found in agreement with theoretical expectations. The presence of argon in air was found to have a negligible effect on the fluorescence yield. We estimated that the systematic uncertainty on the cosmic ray shower energy due to the pressure dependence of the fluorescence spectrum is reduced to a level of 1% by the AIRFLY results presented in this paper.
39534203
Radiation protection problems at a synchrotron radiation facility.
Experiments with synchrotron radiation beams involve risks from ionizing radiation exposure. This report describes the main radioprotection problems around a storage ring working for synchrotron radiation. The dosimetric characteristics of synchrotron light beams are also described. INTRODUCTION SYNCHROTRON radiation is electromagnetic radiation emitted by charged particles, in particular relativistic electrons, moving in curved accelerators, and its name reminds us of this origin. Initially it was considered largely a nuisance, posing severe technical and economic limitations on the energy attainable with circular electron accelerators. Later on, its possible uses became evident, and now synchrotron radiation is widely used as a unique calibrated source in the vacuum ultraviolet and soft X-rays regions. No other source gives such a high intensity together with the possibility of varying the energy over a very wide range. Furthermore, the light is polarized. Synchrotron radiation is emitted tangentially to the orbit of the electrons, and for relativistic energies the emission angle is very small (9 = mc’IE). Storage rings are the machines best suited for the production of synchrotron radiation. When synchrotron radiation is produced by a synchrotron, the electron energy varies rapidly during the acceleration cycle, so that the spectrum of the emitted light is not constant. Furthermore the intensity and the position of the electron beam vary from cycle to cycle and within a cycle. On the other hand, in a storage ring large currents of electrons can be stored and accelerated to the desired energy in a short time, and they keep circulating at that energy for several hours. Beam losses are due only to collisions with residual gas molecules or to instabilities. The synchrotron radiation sources thus generated are characterized by very high intensity and stability in time. Several storage rings in various countries are at the present time dedicated only to the production of synchrotron radiation for physics experiments. An estimate of the power radiated by the electrons moving on their circular orbit can be easily obtained (Ro73; Wi73; Wi76). In fact the energy lost by one electron of energy E in a circle of radius R is given by:
122796566
Cryogenic semiconductor high-intensity radiation monitors
Abstract This paper describes a novel technique to monitor high-intensity particle beams by means of a semiconductor detector. It consists of cooling a semiconductor detector down to cryogenic temperature to suppress the thermally generated leakage current and to precisely measure the integrated ionization signal. It will be shown that such a device provides very good linearity and a dynamic range wider than is possible with existing techniques. Moreover, thanks to the Lazarus effect, extreme radiation hardness can be achieved providing in turn absolute intensity measurements against precise calibration of the device at low beam flux.
122714679
Charge collection efficiency of an irradiated cryogenic double-p silicon detector
Abstract We present results on the measurement of the charge collection efficiency of a p + /n/p + silicon detector irradiated to 1×10 15  n/cm 2 , operated in the temperature range between 80 and 200 K. For comparison, measurements obtained with a standard silicon diode (p + /n/n + ), irradiated to the same fluence, are also presented. Both detectors show a dramatic increase of the CCE when operated at temperatures around 130 K. The double-p detector shows a higher CCE regardless of the applied bias and temperature, besides being symmetric with respect to the polarity of the bias voltage. At 130 K and 500 V applied bias the double-p detector shows a CCE of 80%, an unprecedented result for a silicon detector irradiated to such a high dose.
118438824
Four-quark hadrons: An updated review
The past decade witnessed a remarkable proliferation of exotic charmonium-like resonances discovered at accelerators. In particular, the recently observed charged states are clearly not interpretable as mesons. Notwithstanding the considerable advances on the experimental side, conflicting theoretical descriptions do not seem to provide a definitive picture about the nature of the so-called XYZ particles. We present here a comprehensive review about this intriguing topic, discussing both those experimental and theoretical aspects which we consider relevant to make further progress in the field. At this state of progress, XYZ phenomenology speaks in favor of the existence of compact four-quark particles (tetraquarks) and we believe that realizing this instructs us in the quest for a firm theoretical framework.