Information for HRIBF PAC-9 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 or may be found from our recent newsletters.

Information from previous PACs

PAC-8
PAC-7
PAC-6e
PAC-6

Neutron-rich RIB Development - An update

The last neutron-rich RIB campaign saw several highlights:

• ¹³²Sn yields on target exceeded 10⁵ i/s for double-stripped beams and 8.5x10⁵ i/s for single-stripped beams. The purity of these beams was >95% by using SnS molecular transport.
• ¹³⁴Sn yields on target exceeded 2000 i/s for single-stripped beams and was mixed with 6000 i/s of Sb and Te isotopes. SnS was used.
• ⁸²Ge yields on target exceeded 2x10⁴ i/s for single-stripped beams. The purity was enhanced to 22% by using GeS molecular transport.
• Beams of exotic nuclei such as ^77,78,79Cu have been observed at rates of 1.5 i/s, 0.15 i/s and 20 i/h, respectively. These rates were observed after tandem acceleration to ~3 MeV/u and should be at least a factor of 10 higher since the experiment was overall countrate limited to 5000 i/s. In addition, ⁸⁶Ge has been observed at the 20 i/h level. Although small, these rates are larger than most fragmentation facilities. They are heavily contaminated.
• ¹³²Te single-stripped beam on target had a sustained rate of 3x10⁷ i/s.

For more information contact Paul Hausladen at hausladen@phy.ornl.gov and Dan Stracener at stracener@phy.ornl.gov.

Proton-rich RIB Development - An update

We are planning a series of experiments using ⁷Be beams. A sputter ion source has been developed to hold up to 8 pellets. The anticipated beam intensity is on the order of 10⁸ i/s. We have not produced the ⁷Be here so any potential user will be required to locate a source for the ⁷Be.

Other proton-rich beams are in various stages of development. We anticipate being able to deliver approximately 2x10³ i/s on target of ²⁵Al, 1x10³ i/s on target of ²⁷Si, and 4x10³ i/s on target of ³⁴Cl. It should be noted that these beams have not been accelerated through the tandem and we are assuming 10% transmission to the target. More development work is planned. Significantly higher beam requirements would be viewed as a Letter of Intent. For more information contact Dan Stracener at stracener@phy.ornl.gov.

Generic beamlines

We presently have two beamlines which may support small experimental setups and a third one is in the planning stages. All lines end in either 4-inch conflat and/or 8-inch large flange ports. Cryopumps are presently used for vacuum. One beamline supports the 1-meter scattering chamber (see below) while the other is presently used for fusion-evaporation cross-section measurements. The third beamline will house the Spin Spectrometer (see below) but because it will be the same height as the other beamlines, small user setups should also fit when the Spin Spectrometer is open. For more information contact Felix Liang at liang@phy.ornl.gov and Dan Shapira at shapira@phy.ornl.gov.

Spin Spectrometer

We have plans to rejuvenate the Spin Spectrometer, a 72-element NaI detector array with 4-pi coverage. An initial scan of the detectors suggests most can hold voltage and produce signals. Presently, we anticipate that the energy resolution will be on the order of 10%, sufficient for low countrate experiments with a low density of transitions. The array will be housed on a new beamline (see above). At present, only Letters of Intent should be submitted requiring this detector array. Further investment into the array will depend on the level of interest and initial results. For more information contact David Radford at radford@phy.ornl.gov and

Windowless gas cell

The windowless gas cell will undergo commissioning this summer. Beam has been passed through the cell and reaction products detected at the DRS focal plane. Characterization (density measurements) of the cell will begin shortly; we hope the cell will be used with hydrogen later in the summer. First experiments with the cell are planned for winter. For more information contact Jeff Blackmon at blackmon@phy.ornl.gov.

Forward Array

The forward array is awaiting delivery of constant fraction modules. A prototype CFD was delivered and tested but additional flexibility was desired to make the module useful for a wider range of detectors. We hope the first layer of the forward array will undergo inbeam testing in winter. For more information contact Alfredo Galindo-Uribarri at uribarri@phy.ornl.gov.

Small Csi detector array

A 5-ring CsI array has been ordered and will substitute for the 4-pi CsI HyBall for COULEX experiments. This detector will be used without absorbers for improved response with heavy nuclei. In the COULEX experiments, target atoms which are knocked out of the target are used to identify COULEX events. For more information contact Alfredo Galindo-Uribarri at uribarri@phy.ornl.gov.

Neutron detector array

A 20-element neutron detector array has been purchased from SCIONIX. Each detector contains 1.47 liters of the liquid scintillator LS-301 (similar to NE-213). The detectors are in house, the support structure is under construction, and prototype electrons have been delivered by RIS Corp. We estimate that the array will have an efficiency of around 20%. We hope the array will be available for experiments next winter. For more information contact Chang-Hong Yu at chy@phy.ornl.gov.

Scattering chamber

A 1-meter diameter, 30 cm deep scattering chamber will be installed this summer. At present, it is "bare bones" and users will be expected to help with detector mounts, electrical feedthroughs, etc. We do have a good vacuum system and target ladder. For more information contact Felix Liang at liang@phy.ornl.gov.

Enge in gas-filled mode

The Enge focal plane is being outfitted with a double-sided silicon strip strip detector mounted on a 10-inch OD flange. This detector system will be used for decay studies and in Enge gas-filled mode. For more information contact Felix Liang at liang@phy.ornl.gov or Kris Rykaczewski at rykaczew@phy.ornl.gov

Decay spectroscopy detectors

The proton emitter setup has been expanded to include a four detector Si box situated on the forward side of a DSSD. Proton and alpha particles which exit the DSSD will strike these veto-detectors providing suppression of the low-energy background events. Each detector is 50 mm square and 700 um thick. In addition, a 4.5 mm thick, 45 mm square Si(Li) detector sits behind the DSSD and will be used to detect betas.

The CARDS set-up may also contain BESCA, Bellows Electron Spectrometer for the CARDS Array, a 5-mm thick, 200 mm² Si(Li) detector used to identify conversion electrons. The setup is designed to replace one of the four Clover Ge detector typically used with CARDS. The bellows system allows easy access to the vacuum chamber without warming BESCA.

Microchannel plates at final focus of the RMS

A large MCP detector has been purchased, tested successfully, but then developed a problem. The detector was returned to the manufacturer and new plates were installed. We expect delivery soon and hope that the new large-area MCP will be operational prior to PAC-9. For more information contact Carl Gross at cgross@phy.ornl.gov.

Data acquisition

We are quickly moving to LINUX machines for our data acquisition and analysis computers. These replace our DEC Alpha machines. In the new system, data will be written directly to disk on a new 2-terabyte server. For transport to the user's home, we offer DVD writers (-R,-RW formats) which hold roughly 4.3 GB of data or the usual Exabyte tapes. Users are expected to bring their own DVDs and tapes. Tapes will be slowly phased out. For more information contact Robert Varner at varner@phy.ornl.gov.