Our current major technical project is the update of CHICO to CHICO2. This detector will be commissioned in Fall 2012. CHICO2 is designed to match the angular resolution of the new generation tracking -ray detector array GRETINA. The significant advantages of using the kinematic coincidence method for identifying reaction products using position-sensitive gas detectors include high mass selectivity, large solid angle, high count rates and time resolution. The CHICO2 upgrade was funded primarily by the DOE while the NSF supported the manpower required to perform much of the the upgrade and testing.
The detector uses a theta-phi pixelated cathode that give an angle resolution of 1 degree in theta and 1.4 degrees in phi. A cathode board design has been developed and successful tested that is pixelated in both theta and phi. Like CHICO, the geometry of CHICO2 has each hemisphere containing ten - position-sensitive parallel-plate avalanche detector panels in a conical array. Each of the panels consists of a segmented aluminized stretched polypropylene anode and a delay line cathode. The cathode is segmented into wide stripes for and while is segmented with 1.4 degree resolution. The detection solid angle is of with a minimum flight path of . The anode time resolution is . The measured mass resolution will be for binary collisions.
The following links show a schematic drawing of CHICO2 with the outside dimensions, and the geometry of the CHICO2 cathode. CHICO has 10 clamping lugs around the joint between the front and rear hemispheres of CHICO. Since the diameter of the cavity of the GRETINA detector array is identical to the diameter of the CHICO2 hemispheres it was necessary to remove all but 2 of these clamping lugs around the joint between the front and rear hemispheres to use CHICO2 in conjunction with GRETINA. The cathode boards, transmission lines, fast amplifiers, and digital electronics all were replaced during the CHICO2 upgrade. The CHICO mechanical systems, gas systems, and monitoring equipment all are an integral part of CHICO2.
The longer term goal will be to build a slightly smaller diameter CHICO chamber designed to fit the cavity available using GRETA. Otherwise, this detector, called SuperCHICO, will share all the CHICO2 equipment and development techniques. SuperCHICO will be the ideal heavy-ion detector system required to fully exploit the GRETA -ray tracking detector arrays for binary type reactions that will feature prominently in exotic beam research. The planned capabilities of SuperCHICO are decribed in the slides of a talk at the Future of Gamma-ray Spectroscopy meeting August 2006.