Four methods for determining the composition of low-level uranium- and thorium-chain surface contamination are presented. One method is the observation of Cherenkov light production in water. In two ...additional methods a position-sensitive proportional counter surrounding the surface is used to make both a measurement of the energy spectrum of alpha particle emissions and also coincidence measurements to derive the thorium-chain content based on the presence of short-lived isotopes in that decay chain. The fourth method is a radiochemical technique in which the surface is eluted with a weak acid, the eluate is concentrated, added to liquid scintillator and assayed by recording beta–alpha coincidences. These methods were used to characterize two ‘hotspots’ on the outer surface of one of the 3He proportional counters in the Neutral Current Detection array of the Sudbury Neutrino Observatory experiment. The methods have similar sensitivities, of order tens of ng, to both thorium- and uranium-chain contamination.
A single calorimeter station for the Muon $g-2$ experiment at Fermilab includes the following subsystems: a 54-element array of PbF$_{2}$ Cherenkov crystals read out by large-area SiPMs, bias and ...slow-control electronics, a suite of 800 MSPS waveform digitizers, a clock and control distribution network, a gain calibration and monitoring system, and a GPU-based frontend read out through a MIDAS data acquisition environment. The entire system performance was evaluated using 2.5 - 5 GeV electrons at the End Station Test Beam at SLAC. This paper includes a description of the individual subsystems and the results of measurements of the energy response and resolution, energy-scale stability, timing resolution, and spatial uniformity. All measured performances meet or exceed the $g-2$ experimental requirements. Based on the success of the tests, the complete production of the required 24 calorimeter stations has been made and installation into the main experiment is complete. Furthermore, the calorimeter response measurements determined here informed the design of the reconstruction algorithms that are now employed in the running $g-2$ experiment.
Two precise measurements of the /sup 8/B solar neutrino flux have been made at the Sudbury Neutrino Observatory (SNO) and a third measurement will be made with an array of neutral current detectors ...(NCD). The NCDs are /sup 3/He proportional counters which detect thermalized neutrons liberated by the neutral current reaction /spl nu//sub x/+d/spl rarr//spl nu//sub x/+n+p in SNO's D/sub 2/O. Due to the very low rate of neutrino interactions relative to the rates of other ionizing particles, one major criteria of the array readout system is to facilitate particle identification for the measurement of the solar neutrino flux. Data acquisition at a rate expected to be produced by the neutrino flux from supernovae within our galaxy (10 kpc) is another major requirement. To accomplish these two tasks, a readout system was constructed based upon two distinct pieces of hardware. Digital oscilloscopes are used to maximize particle identification, but are only capable of handling the expected data rate produced by solar neutrinos. Custom-designed VME-based shaping-discriminating-ADC boards measure the total charge of events and are capable of being read out at 20 kHz.
The calorimeter system of the new muon g-2 experiment at Fermilab Alonzi, L. P.; Anastasi, A.; Bjorkquist, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2015, Letnik:
824, Številka:
C
Journal Article
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The electromagnetic calorimeter for the new muon (g–2) experiment at Fermilab will consist of arrays of PbF2 Cerenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. Here, we ...report here the requirements for this system, the achieved solution and the results obtained from a test beam using 2.0–4.5 GeV electrons with a 28-element prototype array.
The beta decay of tritium in the form of molecular TT is the basis of sensitive experiments to measure neutrino mass. The final-state electronic, vibrational, and rotational excitations modify the ...beta spectrum significantly, and are obtained from theory. We report measurements of the branching ratios to specific ionization states for the isotopolog HT. Two earlier, concordant measurements gave branching ratios of HT to the bound HHe\(^+\) ion of 89.5% and 93.2%, in sharp disagreement with the theoretical prediction of 55-57%, raising concerns about the theory's reliability in neutrino mass experiments. Our result, 56.5(6)%, is compatible with the theoretical expectation and disagrees strongly with the previous measurements.
The search for dark matter motivates development of a semiconductor detector system with a very low noise threshold. The CoGeNT and MAJORANA projects both make use of hyper-pure Ge detectors and are ...in principle sensitive to the ionization signals produced by dark matter particles scattering from Ge nuclei if sub-keV thresholds can be achieved.We describe progress toward mitigating noise on several fronts: the lIf noise that is inherent in capacitors and may also be present in the depletion layer of pn junctions, and the aliasing noise that is endemic with FFTs taken digitally over a large frequency range. An operating front-end design with an ENC (equivalent noise charge) of 4.5 electrons RMS has been demonstrated.
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