The design and commissioning of the MICE upstream time-of-flight system Bertoni, R.; Blondel, A.; Bonesini, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2010, Volume:
615, Issue:
1
Journal Article
Peer reviewed
Open access
In the MICE experiment at RAL the upstream time-of-flight detectors are used for particle identification in the incoming muon beam, for the experiment trigger and for a precise timing
(
σ
t
∼
50
ps
)
...with respect to the accelerating RF cavities working at 201
MHz. The construction of the upstream section of the MICE time-of-flight system and the tests done to characterize its individual components are shown. Detector timing resolutions
∼
50
–
60
ps
were achieved. Test beam performance and preliminary results obtained with beam at RAL are reported.
A large volume (4.8 m
3) liquid scintillator detector has been running in Hall C of the Gran Sasso Underground Laboratory since February 1995. This detector is called the “Counting Test Facility” ...(CTF). The main goal of the detector facility is the measurement of ultralow background levels in scintillators and the development of processes able to purify them at this level. The detector has been designed to have exceptional sensitivity using a variety of methods to identify backgrounds. With the CTF, records were achieved in the domain of low background large volume detectors. Limits of 3.5 ± 1.3 × 10
−16 g/g and 4.4
−1.2
+1.5 × 10
−16 g/g for the
238U and
232Th daughters, respectively, and 1.85 ± 0.13 ± 0.01 × 10
−18 for the isotopic abundance of
14C relative to
12C were obtained. These results are very encouraging and point towards the feasibility of low energy, real time scintillation detectors for solar neutrinos, such as Borexino.
A 4.8 m
3 unsegmented liquid scintillation detector at the underground Laboratori Nazionali del Gran Sasso has shown the feasibility of multi-ton low-background detectors operating to energies as low ...as 250 keV. Detector construction and the handling of large volumes of liquid scintillator to minimize the background are described. The scintillator, 1.5 g PPO/L-pseudocumene, is held in a flexible nylon vessel shielded by 1000 t of purified water. The active detector volume is viewed by 100 photomultipliers, which measure time and charge for each event, from which energy, position and pulse shape are deduced. On-line purification of the scintillator by water extraction, vacuum distillation and nitrogen stripping removed radioactive impurities. Upper limits were established of < 10
−7 Bq/kg-scintillator for events with energies 250 keV <
E < 800 keV, and < 10
−9 Bq/kg-scintillator due to the decay products of uranium and thorium. The isotopic abundance of
14C
12C
in the scintillator was shown to be approximately 10
−18 by extending the energy window of the detector to 25–250 keV. The
14C abundance and uranium and thorium levels in the CTF are compatible with the Borexino Solar Neutrino Experiment.
The Borexino detector at the Laboratori Nazionali del Gran Sasso Back, H.; Balata, M.; de Bellefon, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2009, Volume:
600, Issue:
3
Journal Article
Peer reviewed
Open access
Borexino, a large volume detector for low energy neutrino spectroscopy, is currently running underground at the Laboratori Nazionali del Gran Sasso, Italy. The main goal of the experiment is the ...real-time measurement of sub-MeV solar neutrinos, and particularly of the monoenergetic (862
keV)
7Be electron capture neutrinos, via neutrino–electron scattering in an ultra-pure liquid scintillator. This paper is mostly devoted to the description of the detector structure, the photomultipliers, the electronics, and the trigger and calibration systems. The real performance of the detector, which always meets, and sometimes exceeds, design expectations, is also shown. Some important aspects of the Borexino project, i.e. the fluid handling plants, the purification techniques and the filling procedures, are not covered in this paper and are, or will be, published elsewhere (see Introduction and Bibliography).
We report the direct measurement of the {sup 7}Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV ...{sup 7}Be neutrinos is 49{+-}3{sub stat}{+-}4{sub syst} counts/(day{center_dot}100 ton). The hypothesis of no oscillation for {sup 7}Be solar neutrinos is inconsistent with our measurement at the 4{sigma} C.L. Our result is the first direct measurement of the survival probability for solar {nu}{sub e} in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of {sup 7}Be, pp, and CNO solar {nu}{sub e}, and the limit on the effective neutrino magnetic moment using solar neutrinos.
Light propagation in a large volume liquid scintillator Alimonti, G; Arpesella, C; Balata, M ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2000, Volume:
440, Issue:
2
Journal Article
Peer reviewed
The fluorescence light propagation in a large volume detector based on organic liquid scintillators is discussed. In particular, the effects of the fluor radiative transport and solvent Rayleigh ...scattering are emphasized. These processes have been modelled by a ray-tracing Monte Carlo method and have been experimentally investigated in the Borexino prototype which was a 4.3 ton, 4π sensitive detector. The comparison between the model prediction and the experimental data shows a satisfactory agreement indicating that the main aspects of these processes are well understood. Some features of the experimental time response of the detector are still under study.
A search for the decay
μ
+
→
e
+
γ
, performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of
BR
(
μ
+
→
e
...+
γ
)
⩽
2.8
×
10
−
11
(90% C.L.). This corresponds to the measurement of positrons and photons from
∼
10
14
stopped
μ
+
-decays by means of a superconducting positron spectrometer and a 900 litre liquid xenon photon detector.
The Borexino experiment, for the study of solar neutrino physics, requires radiopurity at the level of 5 × 10
−16 g/g
238U equivalent (or 6 × 10
−9 Bq/kg) on a detector mass of many tons of ...scintillator. Feasibility studies are performed in a counting test facility now operating at LNGS, which consists of 4 t of liquid scintillator viewed by 100 photomultipliers and shielded by 100 t of water. The accomplishment of this goal requires the shielding liquid, water, to be at the 10
−13 g/g contamination level (1.2 × 10
−6 Bq/kg) or better. This paper describes the water purification system; it consists of a combination of several purification processes to remove particulate, radioactive ions, dissolved gases and other impurities. Residual contaminations are measured by analytical or direct-counting techniques. For radon measurement, particularly challenging at this low activity levels, a low background counting method has been developed.
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