Information for HRIBF PAC-8 Proposals

mass difference calculator	Estimate isobar contamination
TOPS	Estimate tandem voltage and beam charge state(s)
Neutron-rich beam yields	Estimate yields based on TOPS results

We encourage you to contact us with suggestions for the beams you require to pursue your physics research. Parameters as to what constitutes a suitable beam for the HRIBF may be found in our more recent newsletters.

We ask that you need to be aware that scheduling experiments at our facility is difficult. In some cases such as transfer experiments, suitable equipment is not yet in place to take full advantage of the allocated beam time. In other cases, sufficiently many experiments must be available before it is "cost effective" to schedule a particular RIB ion source or endstation configuration.

Additional information reflecting the present status of equipment and techniques is provided below.

Information from Previous PACs

PAC-7
PAC-6e
PAC-6

Neutron-rich RIB Development - Isobarically pure Sn beams

We are investigating the possibility of increasing yields of our pure Sn beams. Following up on our discovery that SnS+ beams can be extracted from our source with no SbS or TeS components, work done at GSI suggests that the addition of H₂S gas or CS₂ vapors may increase the SnS yields. Based on the sulphur current output from the source, a factor of 3 improvement in intensity may be possible.

CARDS - Clover Array for Recoil Decay Spectroscopy

CARDS was installed at the RMS focal plane in September. Consisting of four Clover Ge detectors in a cross (X) geometry with an optional fifth detector (Clover or Gamma-X) on the beam axis, a highly efficient detection system for recoil decay products is possible. For example, our measured photopeak efficiency was approximately 18% at 80 keV, 8% at 500 keV, and 4% at 1333 keV. Pictures of the set-up, including the newly installed MCP (see below) are available. In September, a 7 us isomer has been discovered in ¹⁴⁰Dy. CARDS will be coupled with the Moving Tape Collector (MTC) in December for a series of beta decay experiments. CARDS equipment, except the Clovers, has been provided by Louisiana State University. In this experiment, more than 20 pnA of 315 MeV ⁵⁴Fe was used.

Microchannel plates at final focus of the RMS

New vacuum chambers have been installed at the final focus of the Recoil Mass Spectrometer which can house position-sensitive-microchannel-plate-plus-thin-foil detector systems (MCP). Three experiments have been performed to date. In addition to the ¹⁴⁰Dy experiment (above), the decay of ^96mAg was studied using CARDS and the RMS in diverging mass mode (only 1.5 masses on the 6 cm foil). Fine structure in proton emission from ^141gsHo has been discovered using the double-sided silicon strip detector (DSSD) with XIA electronics and the RMS is converging mass mode. Here, the MCP was not at the mass focus but much closer to the 4 cm square DSSD. The gas avalanche counter PSAC determined the mass position at the focus and the placement of collimators. The PSAC was then removed. A report on these experiments will be available in the Winter 2002 newsletter.

A larger MCP detector has been purchased and we expect all hardware to be in-house before the PAC meeting. This detector can replace the PSAC in converging mode and we hope will be available toward the end of the period.

Forward Array

Elements of the annular forward array will be tested in February. Several of the double-sided detectors are in-house; each detector consists of 16 annular strips and 8 radial strips which result in 128 pixels. The full array will consist of 12 wedges in two layers creating a large pixellated dE-E telescope array. The CAEN ADCs and TDCs have been incorporated into our data acquisition programs and await testing. The prototype of the shaper has been tested and returned to the vendor for minor modifications. The constant fraction model is in the design stage; initial tests will be performed using in-house level discriminators. It is hoped that a single layer of the full detector will be available to experiments toward the end of period.

(d,p) reactions using the RMS

The astrophysics group's silicon detector array SIDAR was installed at the RMS in July and used to measure the ¹⁸O(d,p)¹⁹O reaction. The RMS selected 5 MeV/u fully stripped ¹⁹O products and delivered them to a silicon strip detector. This test, with the addition of the MCPs with removable foils, should allow full kinematic reconstruction of light radioactive ion (d,p) reactions. Extension to higher mass RIBs will require improved performance of the electrostatic components of the RMS and/or energy degradation of the products. Such studies will benefit from the completion of the forward array (see above).