Forward Indiana Ring Silicon Telescopes

FIRST is intended to study the processes of neck and projectile fragmentation that occurs for peripheral and mid-central collisions between two heavy-ions. This project evolved from the results of our analysis of 114,106Cd + 92,98Mo at E/A=50 MeV. We are presently in the construction phase of this project and anticipate that FIRST will be completed by the Fall of 2003.

As of Aug. 1, 2004 assembly of FIRST is well underway. Almost all mechanical parts have been fabricated. Gluing, wrapping and testing detectors is underway with the help of Dany and Jerome from Universite Laval. The two T1 silicons have arrived and we anticipate the arrival of the T2 and T3 silicons shortly. The FIRST vaccum chamber is expected to be delivered in mid-Aug. We are presently testing electronics and writing the experiment specific DAQ.


1. Rough parameters for FIRST

FIRST will consist of 3 telescopes based upon either a Si-Si-CsI(Tl) stack or just a Si-CsI(Tl) stack for identifying charged particles in Z and A by the DE-E technique. The most forward telescope is designated T1 and the more backward telescopes are T2 and T3 respectively. While T1 utilizes the S2 design from Micron, T2 and T3 are based upon the S1 design to provide the maximum coverage. The parameters of the three telescopes are summarized below.

2. Telescope configuration

Designation First Element Second Element Third Element No. of Concentric rings No. of Pies
T1 200-220 micron Si(IP) 1 mm Si(IP) 2-cm CsI(Tl)/PD 48 16
T2 300 micron Si(IP) 2-cm CsI(Tl)/PD -- 16 16
T3 300 micron Si(IP) 2-cm CsI(Tl)/PD -- 16 16
The active area of a pie of FIRST for the S1 design is approximately 330 mm2

3. Approximate Capacitances of Intrinsic Silicon (Ortec)

Detector thickness (micron) Capacitance (pF/mm2)

4. Experimental setup

Detector Angular range (deg.) Distance from tgt. (in) Angular Resolution (Theta) (deg.)
T1 2.25-7.05 (deg.) 11.02;11.15 (in) 0.025
T2 7.37-14.5 7.31 0.44
T3 15.2-28.5 3.5 0.77
LASSA 33.2-46.8 8 0.8

Detector Angular range (deg.) Measured distance from tgt. (in) Angular Resolution (Theta) (deg.)
T1 2.07 - 6.57 11.453; 11.959 0.094
T2 7.34 - 14.45 7.334 0.45
T3 14.57 - 27.48 3.634 0.82
LASSA 36.38 - 51.11 7.616 0.92

Figure Caption: Galilean invariant diagrams for the 114Cd + 92Mo reaction at E/A = 50 MeV. The acceptances and thresholds for T1,T2,T3,and LASSA have been superimposed on the data.

5. Electronic development

It is presently undecided whether FIRST will use the "conventional" electronics used for LASSA or the new ASICS being developed by the Washington University group for HiRA

6. Photographs of FIRST being constructed

A T2 CsI(Tl) crystal glued to Plexiglas light guide and PIN photodiode
Jerome wrapping the FIRST detectors with Aluminized mylar
Slow signal from a 1 cm x 1 cm PIN photodiode after the WU shaper. A 241Am alpha source illuminated the entire face of a T2 detector. The measured resolution was 8%.