High Voltage Platform System in the Target and Instrumentation Rooms

Injector Beamline on the platform

Transport Beamline from the platform to existing beamline 12

Remote Handling and Localized Shielding in the Target Room

Target Room HVAC System for temperature and humidity control for high voltage operation

Laser Room to provide an operating venue for lasers employed in on-line resonance laser ion sources and in other beam purification schemes employing lasers

Utility systems will be expanded to accommodate the substantial addition of technical equipment

Figure 6-1: Floor map of HRIBF with IRIS2 (shown in red).

7. The FY2006 Budget
(J. R. Beene)

The budget for HRIBF operations and for the HRIBF-based low energy research program for fiscal 2006 has proved to be much more austere than was anticipated at the time of our last Newsletter. The FY2006 budgets for Nuclear Physics adopted by the Congress turned out to be at the level of the President's Budget, and therefore well below the levels in the bills initially passed by either the Senate or the House. The PresidentŐs Budget for Nuclear Physics as a whole was 8.4% below the FY2005 budget. A 1% across the board rescission has since been added. The HRIBF budgets fared slightly better than average, but the effect is still disastrous. The HRIBF operations budget is reduced by 7.8%, while the fixed costs of operations are up more than 6% compared to FY2005. Fixed costs include staff salaries, so-called "background" power costs, and a few other recurring contract costs, and amount to about 90% of the HRIBF operations budget for this year. These fixed costs do not include the direct costs of operating the accelerators for experiments, consequently the funds remaining after fixed costs are highly leveraged in terms of their impact on our ability to deliver beam to experiments. The funds remaining for operations after fixed costs are met will be on the order of half as large as in FY2004 and FY2005. Clearly this will have substantial impact. With adequate funding we expected to continue the steady increase in RIB hours delivered to experiments that we had achieved over the last several years (reaching ~1700 hours in FY2004 before the increase was interrupted by the impact of HPTL completion and maintenance issues). That will clearly not be possible. A more realistic goal under the limitations imposed by the FY2006 budget will be ~1200 hours of RIB on target, and even that will stress us to the limit.

As bad as the impact of the FY2006 budget is on HRIBF operations, the impact on the low-energy research program is much worse. The FY2005 low energy budget was not adequate to cover staff salaries. The existence of a modest carry-over from previous years, some support from HRIBF operations as well as several small addition sources of short-term funds made it possible for us to survive the year without loss of staff. The additional cut of 7% in FY2006, together with no carry-over funds and no hope of help from the already strapped operations budget leaves us in desperate shape. We are far short of meeting even our staff cost, even if optimistic assumptions are made concerning our ability to generate additional short-term funds. This is before any expenses for actually doing research are considered. At this point, a reduction in low energy research staff at HRIBF of at least 20% seems inevitable. This will not only severely impact our in-house research programs, but will also impact the level of service we can provide to outside users of the HRIBF.

8. PAC-12 Results and PAC-13
(C. J. Gross, HRIBF Scientific Liaison)

PAC-12 met December 8-9, 2005, in Oak Ridge and considered 21 proposals and letters of intent which requested 227 shifts of radioactive beams (RIBs), 74 shifts of low intensity stable beams (SIB for RIBs), and 66 shifts of stable beams (SIBs). Of these, a total of 109 RIB shifts (18 provisionally), 19 SIB for RIB shifts, and 21 SIB shifts (+15 additional shifts depending on results) were approved.

Approved experiments requested RIBs of ⁷Be, ^17,18F, ^25,26Al, ⁸⁰Ge, and ¹³²Sn. The total number of accepted proposals was 9, 7 of which were from outside organizations. A letter of intent requesting development of ¹⁰Be beams was also endorsed.

Uwe Greife, previous chair of the Users Executive Committee represented the Users at the meeting.

We wish to thank John Hardy for his service on the PAC; John served as chair of the committee throughout his years of service. He will be replaced on PAC-13 by Brad Sherrill of Michigan State University. We anticipate PAC-13 to occur in late October of this year with proposals due in early September.

9. The HRIBF Strategic Plan
(J. R. Beene)

At the last S&T review of the HRIBF facility and research program, held in November 2004, it was recommended that HRIBF develop a Strategic Plan for the facility and its research program. We had actually begun the development of such a plan a few months earlier and have continued to work on it since. The initial draft was put together by HRIBF management and staff. Extensive comments and suggestions from research staff members and members of the HRIBF Users Executive Committee have also been incorporated. The resulting draft plan was presented to and discussed with the HRIBF Scientific Policy Committee at its meeting on December 9 and 10, 2005; their insights and concerns have helped us to refine the Plan further.

The HRIBF Strategic Plan is intended to serve as a framework to guide the development of HRIBF and its science program and ensure that they are well aligned with the priorities of DOE-NP and the Office of Science. It is divided into three parallel but closely coupled parts, titled Science Opportunities, Experimental Systems, and Facility. The initial part of the Plan lists, in compact form, the overarching scientific goals we hope to achieve at HRIBF, and the corresponding goals for development of experimental hardware and accelerator systems required to enable the science goals. These strategic goals are followed by an "implementation plan" which lists a set of milestones in each of the three areas along a timeline running until 2013. The Science Opportunities, from which the elements in the other two areas derive, are coded to indicate their relationship to the DOE Nuclear Physics Program Milestones. At this point, we are still collecting input from the HRIBF user community and staff, as well as our advisory committees, so the Plan is still considered to be a draft. Even in the long term, however, we will regard this Plan as a living document which will undergo continuous modification to suit changing needs and circumstances.

10. RIA Summer School to be Held at HRIBF
(C. J. Gross, HRIBF Scientific Liaison)

The fifth annual RIA Summer School will be held at HRIBF July 17-23, 2006. The school is organized by the HRIBF, ATLAS, 88-inch Cyclotron Facility, N-division/LLNL, and NSCL and rotates among four of the five laboratories (except LLNL). Between 40 to 50 students are expected to attend lectures in the morning and take part in hands-on demonstrations of experimental equipment and techniques in the afternoon. Time will also be provided for the students to present their research projects. The school hopes to raise sufficient funds so that all local expenses will be covered by the school. For more information go to the school website at www.orau.org/ria/schools.htm.

The timing of the school was chosen so that students may also attend the Nuclear Structure 2006 conference which will also be in Oak Ridge the following week.

11. Nuclear Structure '06 Conference to be Held in Oak Ridge in July 2006

The Physics Division of the Oak Ridge National Laboratory will host the "Nuclear Structure '06" Conference during the week of July 24-28, 2006, in Oak Ridge, Tennessee. This conference is the next one in a series of biennial meetings that have been hosted by North American national laboratories for nearly 30 years. The goal of the conference will be to provide both a broad perspective of the latest progress in experimental and theoretical nuclear structure physics, and to point out the exciting opportunities that lie ahead in the next few years. Detailed information about the meeting will soon become available on the conference web site.

12. Astrophysics Workshop to be Held at HRIBF
(Dan Bardayan)

The Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL) will hold a workshop on nuclear measurements for astrophysics with a special emphasis on the applications of radioactive beams to such studies on October 23-24, 2006.

The purpose of this workshop, hosted by the HRIBF users' executive committee and the Joint Institute for Heavy Ion Research, is to bring together scientists who wish to study nuclear astrophysics with radioactive and stable beams and to acquaint participants with HRIBF's beams and experimental facilities available for such experimental studies.

We plan to organize approximately six sessions discussing nuclear measurements of interest for studying Big Bang Nucleosynthesis, solar burning, hot CNO and rp-process nucleosynthesis in novae and X-ray bursts, and supernovae and the r-process. It is envisioned that the program will be made up of invited and contributed talks. The final session will include an open discussion of future directions for the HRIBF program in nuclear astrophysics and possible collaborative efforts. We welcome your suggestions, both for topics that should be discussed and for speakers. Further, if you would like to make a short contributed presentation, please contact Dan Bardayan. Further details will be announced on the workshop website.

13. Reaction Workshop Held at HRIBF
(D. Shapira)

A workshop on "Near and Sub-barrier Fusion of Radioactive Ions with Medium and Heavy Targets" was held at the ORNL on December 2-3, 2005. There were 32 participants evenly devided between active users and visitors from other institutions in the US and abroad. The idea was to make the community interested in this subject of nuclear physics aware of our capabilities (beams and experimental facilities). A panel at the end of the workshop was convened by the organizers seeking input/consensus on how to best utilize HRIBF resources and cabapabilites to make advances in this field.

Known practicitioners in the field made presentations and served on the panel. These included experimentalists (D. Hinde from ANU, E. Rehm form ANL) as well as theoreticians (B. Balantekin from U. of Wisconsin, P. Moller from LASL, M. Hussein from U. of Sao Paulo).

As expected there is no clear consensus on how to proceed with our local program here, but several ideas were noteworthy. As a result of this workshop contact with future collaborators was established. There were two groups interested in the ⁷Be cababilities at HRIBF. One group was interested in transfer reaction studies and will probably end up doing them at ANL. The other group from INFN-Naples is interested in the quasileastic scattering and breakup of ⁷Be on heavy targets and will submit a proposal to PAC13.

Our local collaboration is expanding and now includes active collaborators from U. of Notre Dame (Kolata), Univ. of Michigan (Becchetti, Amro), Oregon State U. (W. Loveland & co.), UNAM-Mexico (E. Chavez), ANU-Australia (D. Hinde ) and occasional participants from other colleges and universities.

More details about the workshop can be found at its web site.

Feature Articles

RA1. RIB Development
(D. W. Stracener)

Experiments with high-intensity production beams from the ORIC will begin soon at the recently commissioned High Power Target Laboratory (HPTL). The first set of tests will be focused on the production of ²⁵Al and ²⁶Al beams from reactions on silicon. The targets that we plan to test include SiC fibers and pressed pellets of metal silicide powders, such as tungsten silicide and niobium silicide. Other target tests that will be made in the next few months include, thin liquid Ge for production of Se beams, different geometries for the fluorine production target, and high intensity tests on uranium carbide targets with densities that are significantly higher than those presently used.

In the last newsletter we reported on the first experiments with a laser ion source using Ti:sapphire lasers. Another series of tests were recently completed where beams of Cu, Sn, and Ni were produced. This was the first demonstration of three-photon resonant ionization of Cu in a hot-cavity laser ion source using Ti:Sapphire lasers. The ionization efficiency for Cu was 2.4% and, for the first time, frequency quadrupling of the Ti:Sapphire laser was successfully utilized. In addition, we measured the emittance of laser-generated and surface-ionized ion beams, and made measurements of the temporal structures of laser ions with respect to the laser pulse at different source temperatures. The temporal structures of laser ions generated from hot cavities of three different lengths were also measured. These measurements were made in collaboration with Klaus Wendt and his group from Mainz who brought the Ti:sapphire lasers and successfully operated them. A 100 W, 10 kHz Nd:YAG pump laser has been purchased by the ORNL Physics Division and a order for a Ti:sapphire lasers has been placed.

On-line measurements at the On-Line Test Facility (OLTF) during the last few months have included, alpha-particle beams on a liquid Ge target for the production of neutron deficient Se beams, proton-induced fission in a thorium oxide target, release of Re beams from a tungsten oxide target, and measurements of yields of fission fragments from three different UC targets that varied in density and porosity. Analysis of these data sets is continuing and the results will be reported later.

RA2. Accelerator System Status

ORIC Operations and Development (B. A. Tatum)

ORIC provided proton, deuteron, and alpha beams to the RIB injector through the end of September for the production of radioactive ion beams required by the experimental program. In late October and early December, ORIC was utilized for commissioning of the new High Power Target Laboratory. Details of the project and commissioning are presented in a separate article.

The latter part of the year was particularly challenging due to considerable problems with the ORIC rf system. Due to a chain reaction of problems, the system would not operate stably at the 19 MHz frequency required for proton acceleration. With some careful nurturing, we were successful in operating around 12 MHz which is required for both deuteron and alpha acceleration. The difficulties centered on the failure of major components in the rf tuning circuit. Four glass-envelope tunable vacuum capacitors are utilized in the plate circuit of the power amplifier tube. These fragile plate capacitors began to fail with age as some have in the past. Unfortunately, our spare units all showed signs of vacuum degradation due to deteriorated bellows seals. Most of these had never been used but deteriorated on the shelf after many years.

We have recently purchased and installed a set of modern tunable capacitors with ceramic envelopes. Testing of the system with these units has been quite successful, and the rf system appears to be running reliably again following an extended maintenance shutdown.

RIB Injector Operations and Development (P.E. Mueller)

During the period from 1 July 2005 to 1 October 2005, the 25 MV Tandem Electrostatic Accelerator delivered beams of

• 2.7 Mpps [18.7 MV 7+/9+ terminal foil/post foil stripped] 150 MeV pure ¹⁸F,

• 240 kpps [4.58 MV 2+ terminal gas stripped] 14.0 MeV 20:1 ¹⁸F, and

• 100 kpps [5.57 MV 2+ terminal gas stripped] 17.0 MeV 23:1 ¹⁸F to the astrophysics endstation in Beam Line 21, and

• 2 kpps [22.4 MV 14+/25+ terminal foil/high energy foil stripped] 500 MeV 0.36 ¹³⁴Sn,

• 20 kpps [22.14 MV 14+/25+ terminal foil/high energy foil stripped] 489 MeV 0.9 ¹³²Sn, and

• 17 kpps [21.90 MV 13+/24+ terminal foil/high energy foil stripped] 465 MeV 0.9 ¹³²Sn to the time-of-flight endstation in Beam Line 23.

The ¹⁸F beams were produced via the ¹⁶O(⁴He,pn) ¹⁸F reaction by bombarding a fibrous HfO₂ target coupled to a Kinetic Ejection Negative Ion Source (KENIS) with 2-3 uA of 85-MeV ⁴He from the Oak Ridge Isochronous Cyclotron (ORIC).

The tin beams were produced via deuteron induced fission of ²³⁸U by bombarding a uranium carbide coating on a reticulated vitreous carbon fiber target coupled to an Electron Beam Plasma (positive) Ion Source (EBPIS) with 5-6 uA of 43 MeV ²H and passing the positive tin sulfide beam through the recirculating cesium jet charge exchange cell and selecting the negative tin beam resulting from molecular breakup.

Tandem Development (M. Meigs)

The Tandem Accelerator was operated for almost 3000 hours since the last report.   The machine ran at terminal potentials of 1.52 to 24.34 MV and the stable beams ¹H, ⁴He, ¹⁶O, ¹⁷O, ⁴⁰Ca, ⁵⁴Fe, ⁵⁸Ni, ⁸⁰Se, ⁸⁸Sr, ⁹⁰Zr, ¹²⁴Sn, ¹²⁴Te, ¹²⁶Te, ¹³⁰Te and ¹⁹⁷Au were provided.  This is the first time He has been accelerated at our facility.  Radioactive beams of ¹⁸F, ¹³²Sn, ¹³⁴Sn, and ¹³⁴Te accounted for 559 hours of beam on target.  Only two tank openings were necessary during this period with one being a scheduled maintenance opening.  The other tank opening was a quick one-day to replace a failed power supply on the column base quadrupole.  The regular maintenance period allowed replacing bad bearings in the power shafts, replacement of foils in the terminal, refurbishing an ion pump in the terminal, and other minor maintenance and cleaning.  About 195 hours were spent on conditioning with the goal of operation up to 24.5 MV for the neutron-rich program.

RA3. Experimental Equipment - A New Experimental Setup Optimized for (d,p-gamma) Reactions
(M. Johnson, Spokesperson)

A new setup for proton-gamma coincidence measurements in (d,p) reactions has been constructed and tested at HRIBF. One motivation for proton-gamma measurements is to extract neutron capture information for astrophysically important nuclei such as neutron-rich species which may lie on the so-called r-process path. The reactions are performed at the HRIBF by accelerating a nuclear species of interest and impinging the beam onto a deuterated polyethylene target (CD₂). The energy loss of these heavy ions in the target and the unfavorable kinematics results in a practical limit to the achievable energy resolution by detection of charged particles alone. By adding high-resolution gamma-ray detectors, the energy resolution can be improved by almost an order of magnitude.

The (d,p-gamma) setup is pictured in Fig. RA3-1, mounted to the CARDS array. The overall length of the (d,p-gamma) setup is about 3 feet. Additional space is needed on both ends to access the Si detectors within the chamber (discussed below). In all, 5 feet is required for the (d,p-gamma) assembly and accessibilty. Once the Si detectors have been assembled, the access space can be filled using KF-40 pipe for the upstream section and 4" pipe on the downstream section.

Figure RA3-1: Photograph of the (d,p-gamma) setup looking upstream. Seen here is the CARDS array, four Ge clovers, and the vacuum chamber (center of clovers), which house the Si detectors and targets. Preamp modules for the Si telescopes described in the text are mounted (not shown here) on the aft section of the chamber (nearest the photographer). See text for more details.

The (d,p-gamma) setup was designed to use four Ge clovers. In the geometry shown in Fig. RA3-1, the absolute gamma-ray efficiency was measured to be 6.9% at 1.33 MeV. The fronts face of the clovers are approximately 6 cm from the target. The central axis of the clover is perpendicular to the beam axis and is in-line with the target plane. With the use of high-resolution Ge detectors and the close geometry, the largest contribution to the energy resolution comes from Doppler broadening. The Doppler broadening was measured to be 32 keV (FWHM) in each crystal of the clover for recoils of 4-MeV/u A~90 beams onto a CD₂ target.

Protons are detected in a number of Si detectors, mounted within the vacuum chamber. Surrounding the target location is a set of four Si telescopes, configured in a box-like geometry as shown in Fig. RA3-2. The thin transmission detectors closest to the target are 5x5 cm position-sensitive strip detectors. Thick Si 5x5 cm pad detectors back up the thin detectors. The telescope array covers angles from 90 degrees to 135 degrees. The angular resolution is about 2 degrees for this geometry. The preamps are mounted on an additional chamber piece and are attached downstream of the central part of the chamber (visible in Fig. RA3-1).

Figure RA3-2: Photograph of the target location looking downstream. Seen here is a CD₂ target extended into the beam axis. Three other target manipulators are retracted. The bottom manipulator holds a phosphor for beam tuning. Surrounding the target are four Si telescopes. The Ge clovers are on the outside of the chamber walls adjacent to the Si telescopes. Short cables (seen) connect the Si telescopes to the feedthrus to the preamp modules downstream.

For more backward angles, SIDAR is used (Fig.RA3-3a), covering the angular range covered by SIDAR is from 142 degrees to 165 degrees. It is mounted on a flange and slid into the vacuum chamber on two precision slide-rails (Fig. RA3-3b). The preamps for SIDAR are mounted on the flange on which it sits. The solid angle coverage of the entire Si array is estimated at 28% of 4-pi. Also, the SIDAR flange has a viewport which is in-line with the target location, and can be used to tune the beam using a phosphor (see Fig. RA3-2).

Figure RA3-3a: Photograph of SIDAR mounted on the flange. The cables connect the detector wedges to feedthrus to preamp modules which are attached (not shown) on the other side of the flange. In this photograph, the upstream direction is into the plane of the page.			Figure RA3-3b: Photograph of SIDAR being inserted into the vacuum chamber. The feedthrus for the preamp modules can be seen on the left side (exterior) of the flange. Also seen is the viewport (on top of the beamline) for beam tuning. Atop the vacuum chamber is a gate valve which can be connected to a cryo-pump. (No cryo-pump was attached here for the feasibility test discussed in the text.)

Recently, a test run (RIB-131) was performed in which different stable beams were accelerated by the tandem accelerator to test the performance of the (d,p-gamma) setup described above. Fig RA3-4 shows a preliminary plot of excitation energy (derived from proton measurements) versus gamma-ray energy for a run with a ⁹⁰Zr beam onto a 1000 microgram/cm² CD₂ target. One of the benefits of proton-gamma measurements is demonstrated by this plot: for each gamma-ray transition it can be seen at which excitation energy the nucleus was formed. Also, a number of directly populated states are visible, clearly separated in gamma-ray energy, which are not resolved in proton energy alone.

Figure RA3-4: Preliminary results taken from RIB-131. The x-axis is gamma-ray energy (spectrum dispersion is 8 keV/channel), the y-axis is excitation energy extracted from proton energy deposited in the Si array and lab angle (spectrum dispersion is 20 keV/channel). The groupings at x~150, 255, and 325 are proton-gamma coincidences for populating the 1.21-, 2.04- and 2.56-MeV levels. The elongation along the y-axis is due to the comparatively poor resolution of the protons.

Currently, the test runs are being analyzed to determine the full capabilities of the (d,p-gamma) setup. Plans are being made to make new proposals for (d,p-gamma) measurements.

RA4. HRIBF Users Group News
(C. J. Gross)

The HRIBF Users Executive Committee met on December 8, 2006 and elected Robert Grzywacz (University of Tennessee/ORNL) as this year's chair. We thank Uwe Greife (Colorado School of Mines) for his service this past year. During this meeting, the committee discussed the HRIBF strategic plan which shows the integration of science with the facility and instrumentation upgrades into a timeline. This plan, requested by DOE, illustrates how the goals of HRIBF match the goals of DOE.

Letters from the outgoing and new HRIBF Users Executive Committee chairs can be viewed online.

The next users workshop will be on Nuclear Astrophysics and is scheduled for October 23-24, 2006.

RA5. Suggestions Welcome for New Beam Development

HRIBF welcomes suggestions for future radioactive beam development. Such suggestions may take the form of a Letter of Intent or an e-mail to the Liaison Officer at liaison@mail.phy.ornl.gov. In any case, a brief description of the physics to be addressed with the proposed beam should be included. Of course, any ideas on specific target material, production rates, and/or the chemistry involved are also welcome but not necessary. In many cases, we should have some idea of the scope of the problems involved.

Beam suggestions should be within the relevant facility parameters/capabilities listed below.

• The tandem accelerates negative ions only.
• Positive ions may be charge-exchanged or used directly off the platform (E < 40 keV).
• ORIC presently produces up to 52-MeV of ¹H (12 uA); 49-MeV ²H (12 uA); 120-MeV ³He (not yet attempted, costly); 100-MeV ⁴He (3 uA). Higher currents may be possible.
• Typical reactions required to produce more than 10⁶ ions per second are n, 2n, pn, and alpha-n fusion-evaporation reaction channels and beam-induced fission products. More exotic reactions are possible if extremely low beam currents are all that is needed.
• Species release is strongly related to the chemistry between the target material and the beam species. It is best when the properties are different and the target is refractory. Thin, robust targets (fibrous, liquid metals, a few grams per square centimeter) must be able to withstand 1500 degrees Celsius or more.
• Minimum half-life is seconds unless chemistry is very favorable.
• Very long-lived species (T_1/2 > 1 h) are probably best done in batchmode, i.e., radioactive species are produced with ORIC beams and then transported to the ion source where beams are produced via sputtering. Sputter rates of the species and target substrates are important.
• Isobaric separation is possible for light beams (fully stripped ions), while isobaric enhancement may be possible for heavy beams.
• Beware of long-lived daughters or contaminant reaction channels.

RA6. HRIBF Experiments, July through December 2005
(M. R. Lay)