Information for HRIBF PAC-15 Proposals

mass differences, β energies, binding energies	Estimate isobar contamination
TOPS	Estimate tandem voltage and beam charge state(s)
RIB yields	Measured or estimated yields
Velocity calculator	Time-of-flight or Doppler shifts
RMS calculator	Initial parameters used for RMS
TOF (BL-23) calculator	Initial parameters used for Time-of-Flight spectrometer
Ion chamber calculator	Ion chamber with CF4 gas energy loss

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 be aware that scheduling experiments at our facility is not straightforward; several experiments must be available before there is "critical mass" so that 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 on our equipment web pages. You are encouraged to contact the mentor of the equipment should you have any questions. Information from previous PACs is provided below.

IRIS-2

The second RIB production platform will be operational at the end of FY09. All ion sources presently in use at HRIBF will be available at this time. With two operational platforms, transitions between different ion sources can be made quickly resulting in less down-time for ORIC. In addition, RIB delivery can continue during the cool-down and change out of a spent ion source.

The platform of IRIS-2 is much larger, better shielded, and more flexible than IRIS-1. Laser ion sources are being developed for implementation at IRIS-2 but will be incompatible with IRIS-1 due to its small size and location in the building. We anticipate that the first beams utilizing laser techniques (ionization or photodissociation) will be available in FY11.

LeRIBSS - Low energy Radioactive Ion Beam Sepctroscopy Station

LeRIBSS is commissioned and has been used for experiments. Although more experience is necessary, quality data has been obtained using positive ions of ^79-81Zn and negative ions of ^75,77Cu. In the ⁸¹Zn experiment, essentially pure activity samples were obtained even though the intensity of the neighboring ⁸¹Ga is estimated to be a factor of 10⁵ larger. We estimate that the resulting Zn activity was half the total rate. Note that the performance of the isobar separator should be better for positive ions as they do not have to pass through the charge exchange cell when we use the electron beam plasma target ion source. In addition, while positive ions can be expected to have higher yields, there are many more contaminants in the beam often from molecular beams.

The ability to pulse the beam using an electrostatic steerer for measuring the grow-in and decay of the collected activity will be added to the next experiments. We expect pulsing will be possible down to the few millisecond level.

We also expect the small Micro-channel plate (MCP) to become operational this period. With a very thin carbon foil, this MCP is positioned just before the implantation point of the moving tape. The 200-keV ions will pass through the foil and be implanted into the tape. Electrons emitted from the carbon foil will be detected by the MCP and allow fast time correlations between implantation and decay events. This time correlation technique is expected to enhance detection of nuclei very far from stability, ie., low intensity beams of ions with very short halflives.

³Hen β-delayed neutron detector

We expect this ³He ionization counter array for neutrons to be completed this fiscal year and should be available at LeRIBSS and ranging-out experiments in 2010. Each ion chamber 2 foot long and either 1 or 2-inch diameter with a center wire electrode. The 74 stainless-steel tubes filled with 10 atms of ³He gas are held in concentric rings in a high-density polyethylene (HDPE) holder about the beam pipe. These ionization counters detect the neutrons via the ³He(n,p)t resonance reaction. Although these detectors are poor in fast timing applications, they are highly efficient. Our simulations suggest we can expect 75% efficieny for 0.001-1.5 MeV neutrons and 50% efficiency for 5 MeV neutrons.

Electronics upgrade for CHARMS

The old analog electronics for CLARION, HyBall, neutron array and the MCP and ionization chamber detectors located at RMS focal plane will be replaced with GRETINA digital signal processing modules. Each module contains 10 channels which digitize the preamp signals at 100 MHz with 14-bit resolution. Thirty modules have been purchased which offer 300 channels for detectors. It is envisioned that our 11 Clover Ge detectors will each require a single module, HyBall will use 10 modules, and the neutron array will use 2 modules. The two focal plane detectors require two additional modules. The remaining 5 modules can be used for additional detectors such as the zero-degree Bragg detector for RIB sampling and monitoring. We expect this system to be operational in late summer 2009.

Our new beam line (BL-36)

We have begun to purchase equipment for a new beam line positioned next to the Enge spectrometer. Designated as BL-36, we envision the beam line to host ORRUBA charged particle detector array and the rejuvenated Spin Spectrometer. The electronics for the Spin Spectrometer will be the same GRETINA modules described above. We will attempt to configure both arrays to function together which should provide a power system for the study of (d,pγ) in inverse kinematics with RIBs. The beam line is partially funded by the Center of Excellence for Radioactive Ion Beam Studies for Stewardship Science