2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011;
East Lansing, Michigan
Session 1WB: Workshop on Advanced Digital Signal Processing Techniques in Nuclear Science I
8:30 AM–10:00 AM,
Wednesday, October 26, 2011
Room: 104AB
Chair: Sean Liddick, Michigan State University
Abstract ID: BAPS.2011.DNP.1WB.1
Abstract: 1WB.00001 : Gamma ray energy tracking in GRETINA
8:30 AM–9:00 AM
Preview Abstract
Abstract
Author:
I.Y. Lee
(Lawrence Berkeley National Laboratory)
The next generation of stable and exotic beam accelerators will provide
physics opportunities to study nuclei farther away from the line of
stability. However, these experiments will be more demanding on
instrumentation performance. These come from the lower production rate for
more exotic beams, worse beam impurities, and large beam velocity from the
fragmentation and inverse reactions. Gamma-ray spectroscopy will be one of
the most effective tools to study exotic nuclei. However, to fully exploit
the physics reach provided by these new facilities, better gamma-ray
detector will be needed. In the last 10 years, a new concept, gamma-ray
energy tracking array, was developed. Tracking arrays will increase the
detection sensitivity by factors of several hundred compared to current
arrays used in nuclear physics research. Particularly, the capability of
reconstructing the position of the interaction with millimeters resolution
is needed to correct the Doppler broadening of gamma rays emitted from high
velocity nuclei.
GRETINA is a gamma-ray tracking array which uses 28 Ge crystals, each with
36 segments, to cover $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/
\kern-.15em\lower.25ex\hbox{$\scriptstyle 4$} $ of the 4$\pi $ solid angle.
The gamma ray tracking technique requires detailed pulse shape information
from each of the segments. These pulses are digitized using 14-bit 100 MHz
flash ADCs, and digital signal analysis algorithms implemented in the
on-board FPGAs provides energy, time and selection of pulse traces. A
digital trigger system, provided flexible trigger functions including a fast
trigger output, and also allows complicated trigger decisions to be made up
to 20 microseconds. Further analyzed, carried out in a computer cluster,
determine the energy, time, and three-dimensional positions of all gamma-ray
interactions in the array. This information is then utilized, together with
the characteristics of Compton scattering and pair-production processes, to
track the scattering sequences of the gamma rays.
GRETINA construction is completed in March 2011, and extensive engineering
runs were carried out using radioactive sources, and beams from the 88-Inch
Cyclotron at LBNL. The data obtained will be used to optimize its
performance. Then the first scientific campaign will start in March 2012 at
NSCL MSU.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.DNP.1WB.1