Discovery Magazine

Photo Credit: MH

Development of Large-area GEM Detectors with High Spatial Resolution but Low Channel Count.

Different from the HERA electron-proton collider era, the Electron-Ion Collider’s dramatic range in beam kinematics will send hadrons into both the forward and backwards arms in this nuclear physics experiment. Consequently, the arms should be designed to be nearly the same. Planar GEM trackers could cover the forward region at pseudo-rapidities |η|~1-4. Together with nuclear physics colleagues at U. of Virginia, the Florida Tech group is investigating planar low-mass and large-area GEM detector modules of trapezoidal shape that would be arranged in rings around the beam pipe and placed in the forward region of the EIC detector. In the current design for an EIC nuclear physics experiment, two to three ring-shaped detector stations would be positioned at various forward distances from the interaction point. These distances would range from about a meter up to a few meters to cover tracks at higher η.

The current medium-term R&D goal is to perform a slice test of a configuration that uses one trapezoidal GEM detector module from each of these forward detector stations to study the tracking performance. Due to the geometry, the radial dimensions of these detector modules would have to increase with the distance from the interaction point. The GEM detectors closest to the interaction point would extend about 1m in radial direction and the outer detector modules would extend up to about 1.5m radially.

At Florida Tech, we are investigating a particularly cost-effective approach for implementing such GEM forward tracker modules in this new nuclear physics experiment. We are developing increasingly larger prototypes of printed circuit boards with zigzag readout strips for integration into triple-GEM detectors to compare the resulting detector performances with GEM detectors using regular rectangular readout strips. In a one-dimensional readout, the zigzag structure of the readout strips  should allow to measure positions of particles hitting the detector with 3-4 times fewer strips than in a standard GEM detector while maintaining the same position resolution of about 100 microns. This leads to potentially major cost savings for the GEM forward tracker stations in this major new detector for nuclear physics experimentation.

We have integrated a 130-pin Panasonic connector into the design of these pcb so that the strip readout structure can be readily interfaced to our existing analog APV25 frontend amplifier hybrids and to the Scalable Readout System developed by the RD51 collaboration at CERN for experimental particle and nuclear physics. Students are currently designing a medium-size (30cm x 30cm) triple-GEM similar to existing Florida Tech detectors but featuring zigzag strips of different lengths up to 30cm long to investigate noise issues and overall performance in detail. A beam test at Fermilab with these detectors is planned for fall 2013.