Huangshan Chen

Conceptual design of the CBM-TOF wall with real-size high-rate MRPC modules based on the newly developed chinese doped glass

The Compressed Baryonic Matter experiment at the future Facility for Antiproton and Ion Research will use a time-of-flight (TOF) wall for hadron identification, based on the MRPC technology. The wall will be placed at 10m distance from the target covering an area on the order of 150m 2 . We propose here a realistic design for building the TOF wall by resorting to a single technology based on low-resistivity doped glass and relying on small structural modifications of the modules developed and tested during the last two years. The performance of real-size modules is also summarized. XI workshop on Resistive Plate Chambers and Related Detectors (RPC2012) INFN-Laboratori Nazionali di Frascati, Italy February 5-10, 2012

Aging test of a real-size high rate MRPC for CBM-TOF wall

A new kind of low-resistivity glass has been developed. Its volume resistivity is on the order of 1010 Ω cm and multi-gap resistive plate chambers (MRPCs), once assembled with it, can be operated at a charged particle flux in excess of 25 kHz/cm2, with very small charge build-up at the plates. This new technology has a wide range of application in high energy physics experiments such as FAIR-CBM, LHC-ATLAS or Jlab-SOLID, to mention some. In this paper we report on results related to its long-term behavior (aging). A 6 × 2-pad CBM module has been irradiated by X-rays at a mips-equivalent flux of 15 kHz/cm2, for 300 hours and for a released charge totaling 0.22 C (50 mC/cm2). Tested in an electron beam before and after exposure, no degradation of the detector performances could be appreciated. As expected, compared to common glass MRPCs, the newly developed high rate counter also responds faster to sudden irradiation.

Production of long-strip multi-gap resistive plate chamber module for the STAR-MTD system

A new Long-strip Multi-gap Resistive Plate Chamber (LMRPC) prototype with 5 gas gaps has been developed for the Muon Telescope Detector (MTD) of the STAR experiment at RHIC in order to reduce the working High Voltage (HV) of previous design. Technical specifications related to the final infrastructure present in the experiment have motivated this effort. Its performance has been measured with cosmic rays. The efficiency of this prototype can reach 98% and the time resolution is around 95 ps. It shows a good uniformity among strips. The noise level is less than 0.2 Hz/cm2. The signal transmission and crosstalk of the modules was measured with a vector network analyzer, showing a good match with simulations within the amplifier bandwidth. A new cosmic-ray test system with long scintillators has been developed to accelerate the Quality Control (QC) process during the mass production of STAR-MTD. A selection of perpendicular cosmic-ray events for more accurate evaluation of the time resolution is achieved. The time resolution with this method is better, albeit with larger error, than the result obtained without any selection. A new spacer is used, resulting in a much reduced streamer ratio at comparable fields. Thirty-two modules have been built with the new spacer by the middle of April of 2012. They have been tested and they all have passed the QC.

Detectors and Concepts for sub-100 ps timing with gaseous detectors

We give a short compendium of the main ongoing detectors and concepts capable of performing accurate sub-100 ps timing at high particle fluxes and on large areas, through technologies based on gaseous media. We briefly discuss the state-of-the-art, technological limitations and prospects, and a new bizarre idea.

A MRPC prototype for SOLID-TOF in JLab

A prototype of Multi-gap Resistive Plate Chamber (MRPC) for the future SoLID time of flight system at JLab has been developed. The counter, trapezoidal in shape, is assembled with the newly developed low-resistive Chinese glass. It has 10 × 0.25 mm gas gaps and 11 readout strips of different lengths. The strip width is 2.5 cm with a strip-to-strip interval of 3 mm. Preliminary tests performed with cosmic-rays showed an efficiency higher than 95% and a time resolution around 50 ps. Results under diffuse/uniform irradiation performed at JLab with scattered high energy electrons showed a time resolution of 70–80 ps and over-95% efficiency up to an incoming flux of 15 kHz/cm2. These performances meet the requirements of the new time of flight system SoLID-TOF.

A realistic design of the CBM-TOF wall based on modules commissioned in-beam

The Compressed Baryonic Matter experiment at the future Facility for Antiproton and Ion Research will use a time-of-flight (TOF) wall for hadron identification, which is at the moment planned to be based on the Multi-gap Resistive Plate Chamber (MRPC) technology. The wall will be placed at 10m distance from the target, covering an area of the order of 150 m2. Over such an area, it will provide a time-of-flight resolution of 80 ps, by resorting to ca. 50000 RPC cells (in multi-strip or multi-pad configuration). Fluxes of quasi-minimum ionizing particles (γβ≥3) as high as 20 kHz/cm2 can be reached in the central region, corresponding to the low polar angle/high rapidity section. We propose here a realistic design for building the TOF wall by resorting to a single technology based on low-resistivity doped glass and relying on small structural modifications of the modules developed and tested during the last two years. Latest results from the modules are summarized. A comprehensive analytic discussion on the counter performance under non-uniform beams, when neglecting non-local effects, is also presented.

Crosstalk research of long strip timing RPC

The time-of-flight (TOF) wall of CBM is proposed to be assembled with MRPCs. In a relative high particle multiplicity situation (about 20kHz/cm2), multi-hit capability is one of the most demanding requirement of the detector. Crosstalk is an important reason for the deterioration the multi-hit capability of a detector. To reduce the crosstalk level, a kind of shielded long-strip two-end readout MRPC was developed. 1mm width guard strips were added between strips of a 1m-long MRPC. Beam test with 2.5GeV protons was performed in GSI in August, 2009. Horizontal and vertical scans were done. Combined with data from silicon detector, we get the crosstalk between four neighbor strips. The results show that the crosstalk level can be reduced and double hits can affect the time resolution. It also shows that the crosstalk increase with high voltage and decrease with surface resistivity of electrode.

R&D and mass production of LMRPC module for the STAR-MTD system

A new Long-strip Multi-gap Resistive Plate Chamber (LMRPC) prototype with 5 gas gaps has been developed for the Muon Telescope Detector (MTD) of the STAR experiment at RHIC in order to reduce the working High Voltage of previous design. Technical specifications related to the final infrastructure present in the experiment have motivated this effort. Its performances have been measured with cosmic rays. The efficiency of this prototype can reach 98% and the time resolution is around 95 ps. It shows a good uniformity among strips. The noise level is less than 0.2 Hz/cm 2 . The signal transmission and crosstalk of the modules was measured with a vector network analyzer, showing a good match with simulations within the amplifier bandwidth. A new cosmic-ray test system with long scintillators has been developed to accelerate the Quality Control process during the mass production of STAR-MTD. A selection of perpendicular cosmic-ray events for more accurate evaluation of the time resolution is achieved. The time resolution with this method is better, albeit with larger error, than the result obtained without any selection. A new spacer is used, resulting in a much reduced streamer ratio at comparable fields. Fourteen modules have been built with the new spacer by the middle of February of 2012. They have been tested and they all have passed the QC.