Star FGT

The Forward GEM Tracker (FGT) is a detector that was designed and built at Bates as an upgrade to the STAR experiment at RHIC, currently the world’s second most powerful ion collider. Its purpose was to better detect charged particles coming off the heavy-ion at very low angles, where the rate and energy of the particles are extremely high. By employing a new technology, the Gas Electron Multiplier (GEM)[Link][ref#1], we created a durable, low mass detector with high rate capability.

The design of the FGT consisted of 6 carbon fiber-honeycomb disks measuring 80 cm, each populated with 4 GEM detectors. The total of 24 GEM quadrants (plus spares) were designed at Bates and manufactured in our clean room facilities. Many custom tooling and test fixtures were developed specifically for this project. The manufacturing phase took almost 2 years. In addition, Bates engineers collaborated with other national labs and academic institutions to develop front-end and back-end electronics and data-processing software.

Prior to this project, the only source of GEM foils was the CERN laboratory where they were invented, in Geneva, Switzerland. Over the course of FGT development, we worked closely with a local Massachusetts company to develop indigenous GEM-foil production capability in the United States. As a result of this, Tech-Etch, Inc. now operates a full-time GEM foil production line [ref#2], with customers in academia and private industry.

The FGT was installed at STAR in 2011.


  1. F. Sauli - NIM A386 (1997) 531

M. Posik and B. Surrow, Research and Development of Commercially Manufactured Large GEM Foil - arXiv:1411.7243v1 [physics.ins-det] 26 Nov 2014