The workshop "Cancer care: new detector and sensor technologies and their potential impact", organised jointly by the Science and Technology Facilities Council (STFC) and the British Institute of ...Radiology, brought together representatives from the cancer community (clinicians, medical physicists, National Health Service representatives and general practitioners with an interest in cancer) and STFC-supported scientists involved in basic research in physics and technology. The workshop aimed to raise awareness of the cancer challenge, share knowledge and identify novel solutions in the area of detectors and sensors to addressing the cancer challenge. A further aim of this workshop was to commence discussion on the formation of new multidisciplinary community networks. The workshop identified the synergies between the two communities and the potential for developing new collaborative ideas and projects.
Results are presented from the first underground data run of ZEPLIN-II, a 31
kg two-phase xenon detector developed to observe nuclear recoils from hypothetical weakly interacting massive dark matter ...particles. Discrimination between nuclear recoils and background electron recoils is afforded by recording both the scintillation and ionisation signals generated within the liquid xenon, with the ratio of these signals being different for the two classes of event. This ratio is calibrated for different incident species using an AmBe neutron source and
60Co γ-ray sources. From our first 31 live days of running ZEPLIN-II, the total exposure following the application of fiducial and stability cuts was 225
kg
×
days. A background population of radon progeny events was observed in this run, arising from radon emission in the gas purification getters, due to radon daughter ion decays on the surfaces of the walls of the chamber. An acceptance window, defined by the neutron calibration data, of 50% nuclear recoil acceptance between 5
keV
ee and 20
keV
ee, had an observed count of 29 events, with a summed expectation of 28.6
±
4.3 γ-ray and radon progeny induced background events. These figures provide a 90% c.l. upper limit to the number of nuclear recoils of 10.4 events in this acceptance window, which converts to a WIMP–nucleon spin-independent cross-section with a minimum of 6.6
×
10
−7
pb following the inclusion of an energy-dependent, calibrated, efficiency. A second run is currently underway in which the radon progeny will be eliminated, thereby removing the background population, with a projected sensitivity of 2
×
10
−7
pb for similar exposures as the first run.
Dosimetry, the art of dose monitoring, requires a mixture of physics, electronics and engineering. This art is of vital importance in the safety and protection of new energy machines. A case is ...presented for intensified research in the development of dosimeters suitable for the next generation of particle accelerators and fusion reactors.
We report first results from the ZEPLIN I dark matter detector, based on measurement of scintillation pulse shapes in a liquid xenon target of 3.2
kg fiducial mass. Neutron calibration shows nuclear ...recoil pulses to have a time constant
≅
0.5 that of gamma and beta background events. The detector is located in the 2800
mwe depth UK Boulby Mine, and is surrounded by a liquid scintillator Compton veto and passive lead shielding. Three runs totaling 293
kg
d fiducial exposure yielded data consistent with a single population of background pulses, with no significant low energy population of shorter pulses. From the 90% confidence limit on the latter a limit is derived on the spin-independent WIMP-nucleon cross-section versus particle mass with a minimum at 1.1
×
10
−6
pb.
Characterisation of silicon photomultipliers for time-of-flight PET Ahmed, M.; Camanzi, B.; Matheson, J.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2012, Letnik:
695
Journal Article
Recenzirano
The recently developed Silicon Photo Multiplier (SiPM) is a solid state photon detector operating in the Geiger mode. Due to the avalanche nature of its operation, it has a fast response time, ...potentially useful in Time-Of-Flight (TOF) applications. This work is aimed at the application of TOF to Positron Emission Tomography (PET). We have characterised SiPMs from two manufacturers in terms of breakdown voltages, dark count rates and the rise times of the signal in response to pulsed light sources. SiPM timing performances were studied with a Na-22 source, using two-channel systems in which the SiPMs were coupled to scintillator crystals. The best timing resolutions measured were given by Hamamatsu 3×3mm2 area 50μm pixel size SiPMs. These devices gave timing resolutions of 176ps (σ) and 227ps (σ), when coupled to 30mm-long LaBr3(Ce) and 5mm-long LYSO crystals, respectively.
We present results from a GEANT4-based Monte Carlo tool for end-to-end simulations of the ZEPLIN-III dark matter experiment. ZEPLIN-III is a two-phase detector which measures both the scintillation ...light and the ionisation charge generated in liquid xenon by interacting particles and radiation. The software models the instrument response to radioactive backgrounds and calibration sources, including the generation, ray-tracing and detection of the primary and secondary scintillations in liquid and gaseous xenon, and subsequent processing by data acquisition electronics. A flexible user interface allows easy modification of detector parameters at run time. Realistic datasets can be produced to help with data analysis, an example of which is the position reconstruction algorithm developed from simulated data. We present a range of simulation results confirming the original design sensitivity of a few times 10
−8
pb to the WIMP-nucleon cross-section.
MOSFET dosimeters have been exposed to a large range of radiation fields:
192
MeV
positive pions,
500
MeV
electrons,
23
GeV
protons and a wide energy-spectrum of neutrons. This is the first time that ...pion dosimetry with MOSFETs is presented. The response curves of the devices are given, together with an evaluation of their dynamic range, showing that these dosimeters can be successfully used to monitor radiation fields up to very high doses and fluences. In the
500
MeV
electron beam, an irradiation of p
+/n/n
+ diodes together with MOSFETs was also performed. The results of this irradiation show that both types of dosimeters can be used in CMS to monitor in real time the radiation environment.
We present irradiation experiments carried out on RadFETs in the high-intensity T2 neutron beam at the CRC-UCL in Belgium. The aim of the test was to characterize the neutron response of RadFETs in ...view of their use as an integrated part of a radiation-monitoring sensor for the CERN Large Hadron Collider (LHC) experiments. Two types of RadFETs were investigated up to a total neutron fluence of 3/spl times/10/sup 14/ cm/sup -2/ corresponding to a deposited dose of 744 Gy in silicon. The responses of bare devices to neutrons are compared to the commonly used reference measurements with gamma rays. It is found that the gamma ray calibration cannot directly be adopted to convert the RadFET signals into neutron dose. In a second experiment, the influence of a plastic packaging, simulated by polyethylene slabs of different thicknesses, was tested in the neutron beam and compared to GEANT4 Monte Carlo simulations. An increase of the RadFET neutron sensitivity by a factor of up to 7 due to the packaging is found. The influence of these findings on the conception of the radiation-monitoring sensor is discussed.
We present results of a detailed simulation study of neutron background reduction in dark matter detectors based on observation of nuclear recoils below 100
keV. Background rates are estimated for ...neutrons from muons and from natural radioactivity, and with separate Monte Carlo simulations for the underground rock, shielding, and detector components. With optimum shielding combinations, further reduction of background can be achieved with muon and neutron vetos, simulations of the latter giving first estimates of the rejection efficiency as a function of veto geometry. Design options for neutron vetos are also discussed. A detailed tabulation of backgrounds is given, from which it is concluded that the total neutron background can be reduced below the level 10
−4–10
−3
kg
−1
d
−1 needed to detect dark matter particle-nucleon cross sections in the range 10
−10–10
−9
pb, with further reductions attainable in principle with lower-activity detector materials.
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