Conference Paper

Prototype Tests and Construction of the Hadron Blind Detector for the PHENIX Experiment

Dept. of Phys., Brookhaven Nat. Lab., Upton, NY
DOI: 10.1109/NSSMIC.2006.354195 Conference: Nuclear Science Symposium Conference Record, 2006. IEEE, Volume: 3
Source: IEEE Xplore

ABSTRACT A Hadron Blind Detector (HBD) has been constructed as part of the detector upgrade program for the PHENIX experiment at RHIC. The HBD is a proximity focused windowless Cherenkov detector operated with pure CF4 that will be used to detect single and double electrons in relativistic heavy ion collisions and provide additional rejection power against Dalitz pairs and photon conversions. The detector consists of a 50 cm long radiator directly coupled to a set of triple GEM detectors equipped with CsI photocathodes to detect UV photons produced by electrons emitting Cherenkov light. A full scale prototype of the HBD was built and tested in order to study its performance under beam conditions. Tests with the prototype demonstrated good separation between electrons and hadrons using pulse height discrimination and cluster size. The final detector has now been constructed and installed in PHENIX and is presently undergoing commissioning in preparation for its first round of data taking during the next heavy ion run at RHIC. Results of the beam test of the prototype, as well as on the construction and initial testing of the final detector, are presented in this paper.

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    • "Fig. 4 shows the quantum efficiency, measured in vacuum, of a typical CsI photocathode used in our setup. The photocathode was produced using the same facility that is used to produce the photocathodes for the PHENIX HBD detector [5]. All of the photocathodes typically had a quantum efficiency of around 27–30% at 160 nm As shown in Fig. 1, an source was mounted to the back side of the plunger holding the SBD and was used to calibrate the gain of the GEM detector. "
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    ABSTRACT: The absolute photon yield of scintillation light produced by highly ionizing particles in pure CF<sub>4</sub> has been measured using a photosensitive Gas Electron Multiplier (GEM) detector. The detector consists of two standard GEMs and a CsI coated GEM which acts as a photocathode that is sensitive to the 160 nm scintillation light produced in CF<sub>4</sub>. The light yield was determined in terms of the number of scintillation photons emitted into a 4π solid angle produced per MeV of energy deposited in the gas by a 5.5 MeV alpha particle and found to be 314 ±15 photons per MeV. The quantum yield was determined using a fitting method to determine the number of photoelectrons from the measured pulse height distribution, and by an independent method using the measured gain of the GEM detector. The effect of scintillation light in CF<sub>4</sub> on the performance of Cherenkov detectors, such as the PHENIX Hadron Blind Detector (HBD) at RHIC, is also discussed.
    IEEE Transactions on Nuclear Science 09/2010; 57(4-57):2376 - 2381. DOI:10.1109/TNS.2010.2052632 · 1.46 Impact Factor
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    • "Rebuilding the detector required redepositing the CsI photocathodes on all of the top GEMs using the evaporator at Stony Brook [4]. Figure 6 shows the quantum efficiency curve measured for one of the new photocathodes compared to our reference, and indicates that good quantum efficiency was again achieved. "
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    ABSTRACT: The PHENIX Hadron Blind Detector (HBD) was successfully operated during the 2009 high energy polarized proton run at RHIC. This was the first data taking run after the detector was rebuilt following its first commissioning run in 2007. The detector was operated for several months under actual beam conditions and showed greatly improved performance over the commissioning run. Results are given on the operation of the detector, determination and calibration of the gain using scintillation light produced by charged particles in CF<sub>4</sub>, stability of the CsI photocathodes, the ability to identify single and double electrons using the signal from Cherenkov light, and the level of sensitivity of the detector to charged hadrons. A description is also given on the methods used to reconstruct the detector that led to its improved performance.
    Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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    • "However, the measurements have shown conflicting results, particularly regarding the maximum number of photoelectrons that can be extracted from a CsI photocathode surface into various gases and subsequently transported into the gain region of a GEM detector. This process is of great importance for the performance of the PHENIX Hadron Blind Detector (HBD), which uses CsI photocathode GEM detectors to detect Cherenkov photons produced by relativistic particles in a CF radiator in heavy ion collisions at RHIC [9]–[11]. The purpose of this study was to investigate the parameters affecting the photoelectron collection efficiency for CsI photocathode GEM detectors operated in pure CF , in order to better understand this process and to optimize the performance of the HBD. "
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    ABSTRACT: A study has been made of the parameters affecting the extraction and collection of photoelectrons from the surface of a CsI photocathode in a triple GEM detector. The purpose of this study was to optimize the photoelectron collection efficiency and GEM operating conditions for the PHENIX Hadron Blind Detector (HBD) at RHIC. The parameters investigated include the electric field at the surface of the photocathode, the voltage across the GEM, the electric field below the GEM, the medium into which the photoelectrons are extracted (gas or vacuum), and the wavelength dependence of the extraction efficiency. A small, calibrated light source, or ldquoscintillation cuberdquo was used to illuminate a GEM CsI photocathode with a known photon flux produced by the scintillation light from 5.48 MeV alpha particles in CF<sub>4</sub>. The photoelectron collection efficiency was calculated by comparing the number of photoelectrons produced to the number collected at the GEM readout pad. Results are presented on the study of the parameters affecting the photoelectron collection efficiency and the construction and calibration of the scintillation cube.
    IEEE Transactions on Nuclear Science 07/2009; 56(3-56):1544 - 1549. DOI:10.1109/TNS.2009.2020983 · 1.46 Impact Factor
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