Rochester Compact Heavy-Ion Counter: CHICO

University of Rochester

 
 
 
  A schematic view of one half of CHICO showing the 10 PPAC detector panels plus transmission lines to the fast electronics.   Installation of CHICO at Gammasphere by the builders; Mike Simon, Bob Gray, Ching-Yen Wu and Doug Cline  

The position-sensitive heavy ion detector CHICO was developed specifically for use with Gammasphere; it is the fourth generation heavy-ion detector developed at Rochester with NSF support to exploit the advantages of the kinematic coincident technique. CHICO comprises two identical $35.6cm$ diameter hemispherical target chambers, one at forward angles and the other at backward angles. Each hemisphere contains ten $\theta $-$\phi $ position-sensitive parallel-plate avalanche detector panels in a conical array. Each of the panels consists of a $100\mu g/cm^{2}$ segmented aluminized stretched polypropylene anode and a delay line cathode. The cathode is segmented into $1^{\circ }$ wide $\theta $ stripes for MATH and MATH while $\phi $ is measured with $\pm 4.6^{\circ }$ resolution. The detection solid angle is $67\%$ of $4\pi $ with a minimum flight path of $13cm$. The anode time resolution is $\approx 500ps$. The measured mass resolution is $\Delta m/m=5\%$ for binary collisions. During the past decade CHICO has been used in conjunction with Gammasphere for 24 separate experiments involving 58 experimenters from 17 institutions.

A paper describing CHICO has been published. Additional information is available regarding the CHICO fast amplifiers as well as further schematic drawings of CHICO.