Minutes of DRAGON meeting, 23 March 2004. Present: Art Olin (AO), Chris Ruiz (CR), Cybele Jewett (CJ), Dario Gigliotti (DG), Dave Hutcheon (DH), Dave Ottewell (DFOT), Goetz Ruprecht (GR), John D'Auria (JDA), Jonty Pearson (JP), Joshua Slater (JS), Lothar Buchmann (LB), Marcello Pavan (MMP), Mike Lamey (ML), Peter Machule (PM), Mike Trinczek (MT) - recorder. 1. Corrections to Previous Minutes: None. JDA suggests people could read the minutes from time to time... 1a. Catalin Matei, Ph.D. student from Ohio University, is arriving Saturday evening for two weeks and will help with the 12C(a,g) run. LB to supervise. 2. Facility Status: DFOT - The elastic monitors work on the test bench, not in the gas target. There are "flaky" connection problems but he and JP are working on it. Currently using the 241Am alpha source at a modified position in sight of both detectors to test. This will not be possible during the run, so can we easily get a second 241Am "disc" source? DH - Conditioning of ED1/ED2 going slowly. Currently at 158/134kV and need to get to 170/140kV to bend Carbon at (the envisioned) higher energies. ED1 section at 6e-7Torr. PM and/or DFOT to regenerate cryo. Modified CCD camera program provides bigger bullseye and the ability to log info to a file, but currently only for each and every scan. We had wanted to be able to write every ith scan to disk; software company will fix... HOOK UP FCM2!! AO - Can we input CCD info into EPICS history charts? Will investigate. DFOT - Big blower blew its breaker and tripped off. Don't know why. Has been behaving well since. Will investigate. DH - PM has hooked up thermocouple to target box. Room temp is 24 degrees. Needs to be made more robust. PM will take care of it. 3. Upcoming 12C(a,g) Run Preparation: DH - When we run at 4Torr instead of 8Torr, the tune should be roughly 0.75% lower, not 1% lower. LB - We should scan about in 0.25% steps and see what is best. JDA - LB needs to submit Beam Request Form. JDA - Is Paw ready to go? Yes, on midmes01. AO - Do we want to go to isdaq04 and benefit from history monitoring, especially during the 12C(a,g) long runs? Will check. DH - In the future, we will move to isdaq04 to have the Data Acq group support... LB - Will add more detail to the run plan (which was outlined in last week's minutes). 4. Geant Report: JS - Problems! BaF, not BGO, was the default setting for detector array material. This has been corrected and now pair production is roughly 80% (up from the previously-reported, confusingly-low 50%). Why? AO - Explains... there are 2 versions of a DRAGON Monte Carlo. 1. Simple version, used only for gamma-array development 2. Complete Peter Gumplinger version through the spectrometer, "Full Monte" There was a change made to the number of tracking materials in Version 2, thereby changing the BGO ID number to 14 from 10 in Version 1. All the previous gamma-ray efficiency calculations are perfectly fine. DG agrees. Cassie Galt used DG version of 1, so her stuff is okay. Group decides to consolidate the two version. DG, MT, JS, AO will investigate. 4a. DH - David Jenkins has submitted an abstract to a Nuclear Structure conference at ANL on the recent 12C+12C data. DRAGON contribution is being acknowledged as E947 Collaboration. Need to work out criteria for authorship on future papers. MT - Is ast07 (the DRAGON CVS repository for Geant and Root) backed up? Will investigate. [Ed - ast07 is currently not backed up, but will be. To see whether or not a machine is backed up and how to arrange for it to be backed up, go to: http://trbackup.triumf.ca/Backups/ ] 5. Summer Student Projects: Discussion about possible summer student projects based on DH suggestions (below, copied from meeting agenda). DRAGON commissioning: some loose ends? If stable beam time is available this summer, I propose that we make some measurements which would: - double-check unexpected results from the commissioning studies (Sabine Engel's thesis work). This could be part of a publication on DRAGON commissioning using stable beam reactions. - lead to improved beam suppression - determine charge state distributions - provide a good summer-student project A. Yield of the Ecm=259 keV resonance in 21Ne(p,g)22Na We measured wg = 209 +-20stat +-29sys meV (Sabine's thesis p.74) and the literature value is 82.5 +- 12.5 meV. This is far and away the largest discrepancy with previous results in the 6 resonances which we studied. The previous experiment (Goerres et al. Nucl. Phys. A385,57) was 21Ne(p,g) with proton beam and enriched gas target, normalized to a nearby resonance in 14N(p,g) Our measurement could be improved by: (1)measurement, rather than calculation, of the charge state distribution of Na ions at this energy, (2) confirming off-resonance yield is small compared with on-resonance, and (3)better leaky-beam suppression so singles recoil peak isn't sitting on a big tail. B. Energies of the 21Ne(p,g) resonances near 500 keV/u Literature values are Ep=504.3 +-2.0 keV and 524.7 +- 1.5 keV, from an experiment (Antilla et al, Z.Phys. 234,455) using a 21Ne target produced by separation+implantation. We have several times measured energies which are lower by approximately 5 keV/u , for each resonance. For all other resonances where we have made careful energy measurements using MD1, agreement is at the 1 keV/u level. When the surface source is running on OLIS we could do 23Na(p,g) on the strong (1 eV) resonance at Ep = 512.1 +- 0.3 keV. This should make clear whether or not the Antilla numbers are correct. C. Producing a "Golden Tune" for the Scaling program The 21Ne(p,g)22Na resonance at Ecm=259 keV is strong enough that (with a bit of patience) spot sizes at slit locations can be inferred from recoil transmission rates. The maximum recoil cone half-angle is 15 mrad, making it good for verifying first-order focus by quads and aberration reduction by the sextupoles. D. Charge state distribution of Mg ions at 250--330 keV/u The 12C + 12C -> 24Mg + gg experiment requires a number for the charge state fraction of Mg ions between 250 and 330 keV/u. From runs with 24Mg beam we know the distribution at 221 keV/u but for a gas target, not a solid C foil. Without subjecting OLIS to Mg production again, we might be able to measure the required distributions by mounting a thin hydrocarbon film upstream of a thin C foil and make Mg ions via H(23Na,24Mg)g using resonances at Ep=309 and 512 keV. Beams that would be required: 1. 21Ne scanned around 278, 500 and 520 keV/u 2. 23Na at 250, 306, 507 and 490 keV/u Dave H 18 Mar 04 LB - A Geant simulation on the benefits of adding Ge detectors (that Michael Wiescher is willing to send) would be useful. AO - Focal plane detector study? AH is coming for the summer to work on the Cantania detector. This would need some money to order another detector... 6. DG Report on BGO Efficiency DG - Shows plots from his thesis comparing Monte Carlo prediction to measured data of the overall array efficiency with a 244Cm13C source. [Attachment1] It appear that the Monte Carlo is systematically low. He then shows plots where he has allowed a "scaling factor" to adjust the Monte Carlo and obtains the same factor for both source positions. AO - Maybe the source strength has been systematically underestimated? DG - Would like to find a useful reaction with which to test. Thinks protons onto 27Al would provide a perfect isotropic source of gammas. LB - Suggests 27Al(p,g) has a 12MeV line that could be useful. AO - Points out that if we test more sources, then we might be able to tell if the Monte Carlo underestimation is due to the source or to another systematic. This could be a good summer student project, working with DG. Can we get an isotropic source? JDA will investigate. 7. AOB LB - TUDA has given back 4 days of 21Na or 20Na beamtime in May to TRIUMF. Could it be useful to DRAGON? It could be useful to CJ's Ph.D. work. She will consult with UG and decide "what needs doing" and outline a possible run plan at the next DRAGON meeting. Then, DH can ask officially what is possible... Later in the day, JDA sends email detailing summer student projects: Here is a summary of the summer student projects I believed we discussed today. I am not sure if we will have 3 or 4 or 5 students depending upon the financial situation. I also do not know what projects Christof Volkenhuber (arrives in April) or Jac Caggiano (arrives May 1) may wish to get involved with. In addition I do not know if we will run the Ne19 experiment as this depends upon the status of the ECR source. 1. Studies on the Ne21(p,gamma) Reaction/ Supervisor DH/JDA -omega gamma for the 259 keV resonance -resonance energies for certain states -a golden tune in the 250 keV region 2. C12(alpha,gamma) Studies/ Supervisor LB/MT -analysis of data we take in the next month -GEANT simulation calculations including for Ge detector 3. Studies related to Al(p,gamma) reaction Supervisor CR/ML/JDA -analysis of data if we run in July -get IC operational again -get PGAC working with IC 4. Calibration Studies for BGO Supervisor DG/GR/DH -new point source -C12(p,gamma) -N14(p,gamma) 5. Si detector studies with new Catania detector (insufficient funds to buy new detector)/ will not pursue)