HRIBF NEWS

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   Edition 2, No. 3               September 30, 1994            Price: FREE
******************************************************************************* Contents: Editor: Carl J. Gross, Scientific Liaison, cgross@orph01.phy.ornl.gov ******************************************************************************* *******************************************************************************

1. HRIBF Users Meeting at the Williamsburg DNP Meeting.

The HRIBF Users Group Meeting at the fall DNP meeting is scheduled for Thursday, October 27, at 8:30 p.m., in General Lee's Redoubt. It will last an hour and will provide a progress report on the facility. Refreshments will be provided.

Come and show your support!

2. Tandem Operation at 1 MV.

One of the key operating requirements of the facility is the production of RIBs at energies relevant for astrophysics studies. Production of these beams will require the tandem accelerator to operate at very low terminal potentials. This requirement was one of the motivations for replacing the old corona points with more than 3000 resistors last summer. The first measurements using this new configuration have been performed.

The overall transmission efficiency for an 16-O beam was measured in the beam energy range of 2.3 to 50.3 MeV. These measurements indicate that the accelerator can be operated at a terminal potential of 1 MV (2.3 MeV 16-O beams). While it is clear that ultra-low terminal potential operation will require further development work on the terminal potential regulation system, it is encouraging that the overall beam transmission efficiency at 2.3 MeV was observed to be only a factor of two less than that at 50.3 MeV (12.5 MV terminal voltage).

With regard to high voltages, after the installation of the resistors the tandem was quickly conditioned up to 20.7 MV (no beam) with no problems. Conditioning to the highest potentials is scheduled for early 1995.

3. Low Hazard Classification by DOE.

HRIBF has been classified by the Director of the Office of Energy Research, Dr. Martha A. Krebs, as a low-hazard facility. This is an important step as all subsequent safety documents depend upon this classification. All aspects concerning the safe and routine operation of HRIBF are being actively pursued and final approval for the first production of RIBs is expected in November, 1994.

4. New Recoil Mass Spectrometer (RMS) to Operate at Half Power.

After a review of the physics experiments planned for the RMS, it has been determined that nearly all experiments will be satisfied by operating the RMS at less than half the rated power capabilities of the power supplies. In order to avoid added expense, it is proposed that the RMS be connected to the main power system as currently configured. This means that recoils requiring a K greater than 50 cannot be used. (see the review below). You are STRONGLY encouraged to review your experimental plans to ensure that no planned experiment will be compromised by this decision. This power configuration can be changed in the future should higher energy beams become available.

Please contact Carl Gross about your specific requirements for the RMS.

REVIEW:

The original design of the RMS envisioned the use of highly inverse reactions based on high energy, heavy ion beams from the coupled operation of the tandem accelerator and the ORIC booster. Since ORIC is now used to produce RIBs, only tandem beams will be available for the RMS.

The K of a moving ion is given by, K=(Mass*Energy)/(Charge**2). For a "back of the envelope" calculation, assuming the Mass to be 2*Z and the charge is Z/2, K is approximately (8*Energy/Charge).

A REALISTIC CASE:
The reaction of 230 MeV 63Ga with a 12C target, gives a compound nucleus recoil energy of 193.2 MeV. A charge state of 26+ is estimated for a Rb ion of this velocity. Therefore, K = (193.2*75/26**2) = 21.4, well below the planned K=50.

REFERENCES:

J. D. Cole, et al., Nuclear Instruments and Methods Phys. Res. B70, 343 (1992). K. Shima, et al., Atomic Data and Nuclear Data Tables, 51, 173 (1992).

5. In Robinson Hall... Assembly of the RMS.

Robinson Hall has been officially turned over to HRIBF, and the initial surveying of the hall for the location of the various components of the RMS is complete. The assembly of the RMS has started under the supervision of Paul Mantica.

Robinson Hall was officially dedicated on July 11 in honor of the long contributions of Russell L. Robinson to the Holifield Facility. Russell has been with ORNL since 1958 and a driving force that helped make the Holifield Facility into one of the world's premier user facilities for nuclear physics research. Joining HRIBF in this celebration were Russell, his family, friends, former classmates and collaborators.

6. Daresbury Recoil Separator enroute to ORNL

At the present time the Daresbury Recoil Separator (DRS) is aboard the "Atlantic Conveyor" enroute from Liverpool to Portsmouth, Va., where it is scheduled to dock October 7. The expected arrival of the DRS in Oak Ridge is about a week later. This instrument will form the core of an Astrophysics End Station being prepared for HRIBF by the RIBENS (Radioactive Ion Beams for Explosive Nucleosynthesis Studies) Collaboration under the local direction of Michael Smith.

7. Meeting of HRIBF PAC.

The newly appointed HRIBF Program Advisory Committee will hold its first meeting on October 7 in Oak Ridge. During this "get acquainted" session, the PAC members will have the opportunity to provide early guidance for the scientific program of HRIBF. The HRIBF PAC membership is:

     Member               Affiliation                    Service until
    --------             -------------                  ---------------
  S. M. Austin       Michigan State University             1 Oct 1997
  J. R. Beene       Oak Ridge National Laboratory          1 Oct 1996
  R. F. Casten    Brookhaven National Laboratory           1 Oct 1996
  R. M. Diamond   Lawrence Berkeley Laboratory             1 Oct 1996
  W. Gelletly          University of Surrey                1 Oct 1997
  W. C. Haxton       University of Washington              1 Oct 1996
  W. Nazarewicz  Joint Institute/University of Tennessee   1 Oct 1997
  P. D. Parker             Yale University                 1 Oct 1997

8. Announcing HRIBF's World Wide Web (WWW) node.

HRIBF has installed a WWW node which we hope will be accessible by October 15. This node provides information about the facility including such items as the layout of the laboratory and conceptual design of planned experimental equipment. There is a staff directory and a list of the contact personnel, directions to the laboratory, and information needed to arrange a visit. We hope to include schedules for experiments and the next PAC meeting once we are up and running. You will also be able to obtain copies of past newsletters.

To access the node, simply use your favorite WWW browser (e.g. Mosaic from ftp.NCSA.uiuc.edu), open the URL (Universal Resource Locator) to node http://www.phy.ornl.gov/. Not everything is ready but we hope to add things in a timely manner. This is a "living document" so some things will change or be added or deleted. You will find a proposed list of things you will some day be able to find on the node. If you would like to see anything else, please contact Carl Gross.

CHECK US OUT!!!!!!

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Jerry D. Garrett, Scientific Director     |Email:  garrett@orph01.phy.ornl.gov
Mail Stop 6368                            |Tel:    (615) 576 5489

Carl J. Gross, Scientific Liason          |Email:  cgross@orph01.phy.ornl.gov
Mail Stop 6371                            |Tel:    (615) 576 7698

Holifield Radioactive Ion Beam Facility   |Tel:    (615) 574 4113
Oak Ridge National Laboratory             |Fax:    (615) 574 1268
Oak Ridge, TN 37831