R. P. Pisani

Construction and expected performance of the hadron blind detector for the PHENIX experiment at RHIC

A new hadron blind detector (HBD) for electron identification in high density hadron environment has been installed in the PHENIX experiment at RHIC in the fall of 2006. The HBD will identify low momentum electron-positron pairs to reduce the combinatorial background in the e + e - mass spectrum, mainly in the region below 1 GeV/c 2 . The HBD is a windowless proximity-focusing Cherenkov detector with a radiator length of 50 cm, a CsI photocathode and three layers of gas electron multipliers (GEM). Pure CF 4 is used as a radiator and a detector gas. This proceeding describes the construction details and the expected performance of the HBD.

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

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.

The PHENIX Time Expansion Chamber

Abstract The TEC/TRD subsystem will track all charged particles and contribute to the particle identification by the measurement of energy loss. The design, construction and testing of the TEC chambers are described.

A hadron blind detector for the PHENIX experiment at RHIC

A hadron blind detector (HBD) is being developed for an upgrade of the PHENIX experiment at RHIC. The HBD is a windowless Cherenkov detector, operated with pure CF/sub 4/ in a special proximity focus configuration. The detector consists of a 50 cm long radiator, directly coupled to a triple GEM detector which has a CsI photocathode evaporated on the top surface of the uppermost GEM foil, and a pad readout at the bottom of the GEM stack. Detailed studies of the detector performance, including hadron rejection, figure of merit, N/sub 0/, number of photoelectrons and efficiency are presented. These studies include measurements performed with a UV lamp, an /sup 55/Fe X-ray source and an /sup 241/Am alpha source. Results will also be given on aging studies of the GEM foils and the CsI photocathode in pure CF/sub 4/.

A VUV gas transmission monitor and recirculating gas system for the PHENIX hadron blind detector

The PHENIX Hadron Blind Detector (HBD) is a high performance Cherenkov counter that uses pure CF4 to detect electrons in relativistic heavy ion collisions at RHIC. It requires extremely high purity gas in order to achieve a high photoelectron yield, preserve the quality of its cesium iodide photocathodes, and maintain stable gas gain in its GEM detectors. In particular, water and oxygen at even the few ppm level can cause significant optical absorption in the wavelength range from 120-180 nm, which is the region of sensitivity of the Csl photocathodes. In order to ensure good optical transparency and low water and oxygen content of the operating gas, a transmission monitor has been constructed to measure the transmittance of the input and output gases of the HBD. The monitor is based on a McPherson 234/302 VUV spectrometer, along with a custom, computer controlled movable mirror system to measure the transmittance of the gas flowing to and from the detector. The monitor is used in conjunction with a recirculating gas system that is designed to supply high purity gas with minimal consumption. Both the transmission monitor and the recirculating gas system are described, along with their performance when used with the Hadron Blind Detector during the 2006-07 heavy ion run at RHIC.

Initial performance of the PHENIX Hadron Blind Detector at RHIC

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 CF4, 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.

A faster digitizer system for the Hadron Blind Detector in PHENIX

A Hadron Blind Detector (HBD) has been installed in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). A 2300 channel compact 12-bit 60 MHz digitizer system has been built to read the HBD system. The raw signals are shaped with 70 ns rise time and are directly digitized. The time and charge of the raw signals can be calculated from the multiple samples. The system is designed to handle Level 1 (L1) trigger rates up to 25 kHz with 5 L1 event buffers. Large amounts of data are generated after the ADC. Issues regarding clock distribution, data handling, event buffers, and L1 trigger primitive generations have been addressed. The overall system performance will also be discussed.