Cherenkov detectors in the alpha magnetic spectrometer Barao, F
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2000, Letnik:
454, Številka:
1
Journal Article
Recenzirano
Cherenkov detectors have been widely used in High Energy Physics and Astrophysics. Their use allows to measure the velocity and charge magnitude of charged particles in a very accurate way, leading ...to particle identification. The Alpha Magnetic Spectrometer (AMS) whose test flight took place in June 1998, was equipped with an Aerogel Threshold Counter mainly for antiproton identification purposes. Additionally, the counter was also used to improve the selection of positrons. In a second phase, the AMS spectrometer capabilities will be extended through the inclusion of a Ring Imaging Cherenkov detector.
Characterization study of silica aerogel for Cherenkov imaging Sallaz-Damaz, Y.; Derome, L.; Mangin-Brinet, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2010, Letnik:
614, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Different methods to measure the characteristics of silica aerogel tiles used as Cherenkov radiator in the CREAM and AMS experiments have been investigated to optimize the detector performances. The ...measurement accuracy dictated by the physics objectives on the velocity and charge resolutions set stringent requirements on the aerogel refractive index determination, namely
Δ
n
∼
1.5
×
10
−
4
and
Δ
n
∼
5
×
10
−
4
for the AMS and CREAM imagers, respectively. The matching of such accuracies for this material turned out to be a metrological challenge, and finally led to a full R&D program, to develop an appropriate characterization procedure. Preliminary studies performed with a standard refractive index measurement technique (laser beam deviation by a prism) have revealed a significant systematic index nonuniformity for the AMS tiles at a level
(
10
−
3
)
, not acceptable considering the aimed accuracy. These large variations were confirmed in a beam test. A second method, mapping the transverse index gradient by deflection of a laser beam entering normally to the tile has then been developed. It is shown that this procedure is suitable to reach the required accuracy, at the price of using both methods combined. The several hundreds of tiles of the radiator plane of the CREAM and AMS Cherenkov imagers were characterized using a simplified procedure, however, appropriate for each case, compromising between the amount of work and the time available. The experimental procedures and set-ups used are described in the text, and the obtained results are reported.
The Alpha Magnetic Spectrometer experiment to be installed on the International Space Station will be equipped with a proximity focusing Ring Imaging Cherenkov (RICH) detector, for measurements of ...particle electric charge and velocity. In this note, two possible methods for reconstructing the Cherenkov angle and the electric charge with the RICH are discussed. A Likelihood method for the Cherenkov angle reconstruction was applied leading to a velocity determination for protons with a resolution of around 0.1%. The existence of a large fraction of background photons which can vary from event to event implied a charge reconstruction method based on an overall efficiency estimation on an event-by-event basis.
In-beam tests of the AMS RICH prototype with 20 A GeV/c secondary ions Baret, B.; Aguayo, P.; Benitez, M.A. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
06/2004, Letnik:
525
Conference Proceeding
In-beam aerogel light yield characterization for the AMS RICH detector Aguilar-Benitez, M.; Arruda, L.; Barao, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2010, Letnik:
614, Številka:
2
Journal Article
Recenzirano
The ring imaging Cherenkov (RICH) detector of the AMS-02 spectrometer provides a very precise measurement of the electric charge and velocity. The RICH detector is composed of a conical reflector ...ended on top by a dual radiator plane made of sodium fluoride and aerogel, and at the bottom by a detector plane made of pixelized photomultipliers. The vast majority of the events (
∼
90
%
) that are collected in the RICH cross the aerogel radiator. Therefore, the choice and characterization of the aerogel radiator is essential for reaching the design goals. A prototype of the RICH detector was built for both concept proof and testing of the different elements. Beam tests with the RICH prototype and using several aerogel radiator samples were performed at CERN in 2002 and 2003. This note summarizes the method used and the results obtained for the light yield of different aerogel samples.
The AMS-01 Aerogel Threshold Cherenkov counter Barancourt, D; Barao, F; Barbier, G ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2001, Letnik:
465, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The Alpha Magnetic Spectrometer in a precursor version (AMS-01), was flown in June 1998 on a 51.6° orbit and at altitudes ranging between 320 and
390
km
, on board of the space shuttle Discovery ...(flight STS-91). AMS-01 included an Aerogel Threshold Cherenkov counter (ATC) to separate
p
̄
from e
− and e
+ from p, for momenta below
3.5
GeV/c
. This paper presents a description of the ATC counter and reports on its performances during the flight STS-91.
Transjugular intrahepatic portosystemic shunt (TIPS) has been the therapeutic option for severe decompensation of chronic liver disease and as a bridge to liver transplantation. The aim of this study ...was to analyze the complications of this procedure. The records of 47 patients (39 men) of mean age 48 years underwent TIPS procedures from 1998 to 2003 were reviewed. Forty-one patients received 45 successful TIPS; it failed in six patients. Improvement was observed in 20 of 28 patients with upper gastrointestinal bleeding (71%); 9 of 11 with ascites (82%); and 5 of 8 with impaired renal function (62%). The Child-Pugh scores improved in 6 of the 47 patients (13%). Transplantation was performed in 11 patients (23%). The complications were: encephalopathy (49%); infection (19%); renal failure (17%); TIPS migration to the portal vein (4%) and to the right atrium (4%). Mortality was 32% (15/47) over 3 months. Eight patients developed active bleeding during TIPS installation requiring mechanical ventilation and intensive care, and died within the first week. Other causes of death were sepsis (
n = 2), liver failure (
n = 1), accidental puncture of the Glisson's capsule leading to intra-abdominal bleeding (
n = 1) and refractory upper gastrointestinal bleeding (
n = 3). The latter four patients had TIPS placement failure. In conclusion, TIPS produced clinical improvement among 51% of patients with complications in 49%. The main complications were encephalopathy (49%), infection (19%), and renal failure (17%). The 3-month mortality rate after TIPS placement was 32%.
Partial budgeting was used to compare net incomes of high-yielding Holstein cows fed either a total mixed ration (TMR), a pasture-based diet, or a combination of both. Variables included in the ...analysis were milk income, feed, feeding, manure handling, fencing, and water system expenses (revenues and costs based on 2000 values). Base data were from 45 Holstein cows (109 days in milk), assigned to one of three dietary treatments: TMR (nongrazing with TMR ad libitum), pasture plus TMR (pTMR, with pasture in the day and TMR at night), or pasture plus concentrate (PC, pasture twice daily plus 1kg of concentrate/4kg milk). Data from those groups were projected to a case-study herd of 70 cows and subjected to sensitivity analysis at varying milk prices and feed and pasture costs. Although costs per kilogram of milk produced were lowest for PC cows, cows on TMR had the highest net income per cow per day ($5.61) because of higher yields of milk (38.1kg/d) and milk components (1.24kg/d of fat, 1.13kg/d of true protein), although expenses were highest among all systems ($4.12). Cows on the PC had lower daily net income ($5.31) due to lower yields of milk (28.5kg/d) and milk components (0.89kg/d of fat, 0.79kg/d of true protein) even though expenses were also lowest ($2.57). Cows fed the pTMR were intermediate in production (32.0kg/d of milk, 1.06kg/d of fat, 0.93kg/d of true protein) but had similar daily net income per cow ($5.28) to the PC cows but were lower than the TMR cows. Sensitivity analysis showed that the TMR system was more profitable than the pTMR and PC systems, with expenses considered, except at combinations of lower milk prices and higher feed costs. Differences between the pTMR and PC systems were less, with PC being more profitable in half of the scenarios, particularly at lower milk prices and higher feed costs.
Prototype study of the Cherenkov imager of the AMS experiment Aguayo, P.; Aguilar-Benitez, M.; Arruda, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2006, Letnik:
560, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The AMS experiment includes a Cherenkov imager for mass and charge identification of charged cosmic rays. A second generation prototype has been constructed and its performances evaluated both with ...cosmic ray particles and with beam ions. In-beam tests have been performed using secondary nuclei from the fragmentation of
20
GeV
/
c
per nucleon Pb ions and
158
GeV
/
c
per nucleon In from the CERN SPS in 2002 and 2003. Partial results are reported. The performances of the prototype for the velocity and the charge measurements have been studied over the range of ion charge
Z
≲
30
. A sample of candidate silica aerogel radiators for the flight model of the detector has been tested. The measured velocity resolution of the detector was found to scale with
Z
-
1
as expected, with a value
σ
(
β
)
/
β
≈
0.7
–
110
-
3
for singly charged particles and an asymptotic limit in
Z of 0.4–
0.6
×
10
-
4
. The measured charge resolution obtained for the
n
=
1.05
aerogel radiator material selected for the flight model of the detector is
σ
(
Z
)
=
0.18
(statistical)
⊕
0.015 (systematic), ensuring a good charge separation up to the iron element, for the prototype in the reported experimental conditions.
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