15 research outputs found
Pulse Shape Analysis with scintillating bolometers
Among the detectors used for rare event searches, such as neutrinoless Double
Beta Decay (0DBD) and Dark Matter experiments, bolometers are very
promising because of their favorable properties (excellent energy resolution,
high detector efficiency, a wide choice of different materials used as
absorber, ...). However, up to now, the actual interesting possibility to
identify the interacting particle, and thus to greatly reduce the background,
can be fulfilled only with a double read-out (i.e. the simultaneous and
independent read out of heat and scintillation light or heat and ionization).
This double read-out could greatly complicate the assembly of a huge,
multi-detector array, such as CUORE and EURECA. The possibility to recognize
the interacting particle through the shape of the thermal pulse is then clearly
a very interesting opportunity.
While detailed analyses of the signal time development in purely thermal
detectors have not produced so far interesting results, similar analyses on
macro-bolometers (10-500 g) built with scintillating crystals showed that
it is possible to distinguish between an electron or -ray and an
particle interaction (i.e. the main source of background for 0DBD
experiments based on the bolometric technique). Results on pulse shape analysis
of a CaMoO crystal operated as bolometer is reported as an example. An
explanation of this behavior, based on the energy partition in the heat and
scintillation channels, is also presented.Comment: Presented at the 14th International Workshop on Low Temperature
Detectors, proceedings to be published in the Journal of Low Temperature
Physic
Spatially-resolved measurement of optically stimulated luminescence and time-resolved luminescence
Spatially-resolved measurements of optically stimulated luminescence (OSL) were performed using a two-dimensional scanning system designed for use with planar samples. The scanning system employs a focused laser beam to stimulate a selected area of the sample, which is moved under the beam by a motorised stage. Exposure of the sample is controlled by an electronic shutter. Mapping of the distribution of OSL using a continuous wave laser source was obtained with sub-millimeter resolution for samples of sliced brick, synthetic single crystal quartz, concrete and dental ceramic. These revealed sporadic emission in the case of brick or concrete and significant spatial variation of emission for quartz and dental ceramic slices. Determinations of absorbed dose were performed for quartz grains within a slice of modern brick. Reconfiguration of the scanner with a pulsed laser source enabled quartz and feldspathic minerals within a ceramic sample to be differentiated using a single stimulation wavelength by measuring the time-resolved luminescence spectrum
First test of a cryogenic scintillation module with a CaWO4 scintillator and a low-temperature photomultiplier down to 6 K
Future cryogenic experiments searching for rare events require reliable,
efficient and robust techniques for the detection of photons at temperatures
well below that to which low-temperature photomultipliers (PMT) were
characterised. Motivated by this we investigated the feasibility of a
low-temperature PMT for the detection of scintillation from crystalline
scintillators at T = 6 K. The scintillation module was composed of a CaWO4
scintillator and a low-temperature PMT D745B from ET Enterprises. The PMT
responsivity was studied at T=290, 77 and 6 K using gamma-quanta from 241Am (60
keV) and 57Co (122 and 136 keV) sources. We have shown that the low-temperature
PMT retains its single photon counting ability even at cryogenic temperatures.
At T = 6 K, the response of the PMT decreases to 51 +- 13 % and 27 +- 6 % when
assessed in photon counting and pulse height mode, respectively. Due to the
light yield increase of the CaWO4 scintillating crystal the overall
responsivity of the scintillation modules CaWO4+PMT is 94 +- 15 % (photon
counting) and 48 +- 8 % (pulse height) when cooling to T = 6 K. The dark count
rate was found to be 20 s-1. The energy resolution of the module remains
similar to that measured at room temperature using either detection mode. It is
concluded that commercially available low-temperature PMT are well suited for
detection of scintillation light at cryogenic temperatures
Electron and Gamma Background in CRESST Detectors
The CRESST experiment monitors 300g CaWO_4 crystals as targets for particle
interactions in an ultra low background environment. In this paper, we analyze
the background spectra that are recorded by three detectors over many weeks of
data taking. Understanding these spectra is mandatory if one wants to further
reduce the background level, and allows us to cross-check the calibration of
the detectors. We identify a variety of sources, such as intrinsic
contaminations due to primordial radioisotopes and cosmogenic activation of the
target material. In particular, we detect a 3.6keV X-ray line from the decay of
41-Ca with an activity of (26\pm4)\mu Bq, corresponding to a ratio
41-Ca/40-Ca=(2.2\pm0.3)\times10^{-16}.Comment: 7 pages, 12 figure