Rutgers Nuclear Physics Group
Gamma Sphere Experiments

• Eurogam
  Jan.1993 (Daresbury) Feasibility study.
• Gamma sphere (Berkeley)
  1. Test run Oct 1995
  2. GS 55    May 1996
  3. GS 120  Jul 1997 (Jul.31 - Aug.4)

Open detector array with chamber used in g-factor experiments

In all experiments ^193,194Hg was produced in the reaction ¹⁵⁰Nd(⁴⁸Ca,xn)Hg at about 204 MeV.

Data were written onto EXABYTE tapes. Pre processed event data were then written to DLT tapes using a new event structure  for the analysis.

GS 55

Gamma sphere had 90 detectors operational. The specific setup information is compiled in a header file, detid.h.. The detector configurations and placements are presented in lookup tables.
The efficiency data are parameters to be used with xclio.

The 'original' recorded events were reduced to essentially the following information:

• header word (including field direction and number of recorded detectors)
• number of total hits (multiplicity)
• list of detector with/and 'clean' energies

The results of the analysis are published:
"First direct measurements of g factors of three superdeformed bands of ¹⁹⁴Hg"
Phys. Rev. C58, R2640 (1998)

GS 120

This time 103 detectors of the 110 possible were implemented.
The setup is found in detid.h. The experiment design was for a target with a gap between the ¹⁵⁰Nd layer and the Gd (ferromagnet), so that only nuclei while in the 3 lowest states of a SD band interact with the Gd.

The picture here shows the velocity of the nuclei taken from the Doppler shift of the SD1 band. In GS 120 (blue) all SD1 states decay while the nucleus is still in flight. The gap was too large. The red points are taken from experiment GS 55.

A summary can be found in the postmortem by Noemie Koller