From dauria@sfu.ca Tue Aug 27 09:57:53 2002 Date: Fri, 23 Aug 2002 00:19:07 -0700 From: John D'Auria To: Internal: ; Subject: Minutes of DRAGON meeting of Aug. 20 (note to all: These minutes are very informal and I am circulating them to the Internal group only. These should not go any further without some serious editing. jda] Minutes Tuseday August 20 Present: JD, DO, DH, MC, JR, CJ, AL, SB, JF(recorder), CW, ML, LB, AO Changes to last minutes: (recorded by jda) Business Arising: -It was noted that CJ is looking into the charge state distributions from the runs with the IC. -w.r.t item 4b from last meeting - 17C efficiency test will be happening in the next day or two. There was a problem with the vacuum system -there was a comment that the ECR is not yet ready for online and won't be running this fall - Version 2 of the ECR has an efficiency significantly less than the previous version Business as Scheduled: 1) State of the Facility, Immediate Plans: -Timing resolution tests will be done in-situ with the DSSSD and the MCP over the next couple of weeks. (The tests don't have to wait for the DSSSD cooling system) -The ion chanber will need to be taken off. We will prevent the thin window from breaking by using a blanking flange and unplugging the roughing pump associated with the IC. This will be done today. -A request for stable beam can be put in for after the MCP tests are completed the discussion of this will be delayed until we have some idea how long the MCP test are going to take. -the local TOF approach can be tested if the MCP tests can eliminate the current double peak and if the resulting timing resolution is good enough. 2) Radioactive beam time has been tentitivly scheduled: -Expt:824 21Na Starting around Nov27 and going for 2 weeks. -We will want to request stable beam before hand for preliminary tests. 3) Results from the runs using the IC: -Two charge state distributions of the number of recoils/elastics have been plotted, both have a definite max. <- these should be compared to Wenjie's formula. -Coincidences between the recoils and gammas were seen -CJ to look at gamma coincidence data as it's the only measure of time resolution -FWHM of the timing peak ~300ns which is more than the recoil-ion time spread. this is limited by the drift time of the electrons 4) Publications: Facility Paper: -Aspect ratio of pictures strange but otherwise close to a final draft -Art and Shawn still have suggestions to submit -There are words on measuring the energy with MD1 -Comments and discussion on including energy detemination: -Energy determination should be a whole section -Most things dealt with to this point have been more concerned with yield than with energy -It should go out prior to the first paper published which specifically deals with energy -Possibilities: -forgo MCP tests and test for energy, thus delay publishing -Include in first paper published which specifically deals with energy -publish something short on the energy calibration -include in Sabine's NIM (EMIS-14) paper --Final decission: The paper will be submitted soon with little mention of the energy. It will be measured but MCP tests still have priority 5) Dave's presentation related to the paper on the 822 keV study: The Beta monitor and the Elastic monitor have proved to be useful for more things than first intended: Beta monitor as a substitute for the Elastics monitor: -takes a measure of beam stopped on the left slit. Should hit pretty well in the middle of the slit area -Q: How much sensitivity is there to the setting of the slits? -A: Don't think beyond a couple of %, should be easy enough to check by opening/closing the Mass slits -as long as centring of beam at the Mass slits is done correctly it should always go to the same place, ~2cm off center, when ED1 tune is changed from beam to recoils. -For the infamous run 6214, some of the B may have gone through the 'hole' which might be why the B and elastics don't agree -There was, for some reason, much more beam spill in the spring runs in low energies compared to the fall, making it very hard to subtract background from the Elastic monitor spectra. -Conclusion: B monitor can measure beam intensity so if the scattering in the gas target is not Rutherford, the B monitor can be substituted for the elastic monitor. Use of the elastic monitor time info to infer changes in the beam energy: -Had used 21 meters for the length, probably better to use 22m. -The slope was fixed and not a best fit of the data points. -If for some reason the C slits are offset so the tune through MD1 is not right, the B monitor will not be effected provided ED1 was set to centre beam on the M slits. -It would be nice to have an explanation of the scatter in MD! settings w.r.t. the elastic energies. The 21Na(p,g) 822 keV reasonance: -if we're willing to not claim a hard value of Gamma the capture data should give a publishable omega-gamma -we can fairly well define an area under the yield curve -there is no doubt we still have substantial yield at ~885 keV/u and ~840keV/u -Our sensitivity to Gamma is blunted by losing 14keV/u through the target, if we ran 1.5Tor instead of 4.5Torr it would be easy to distiguish a Gamma of 10 keV and easier (but still tough) to distinguish a Gamma of 15 from one of 18 keV. -a Gamma closer to TUDA's value is not unacceptable when looking at the capture plots but a stretch in the elastic scattering from DRAGON's Elastic monitor. -changing pressure may not have a large effect on elastics as they already see a thin target -We should also not be too taken in by the small statistical error bars, it is possible that there is a systematic problem which is as important or perharps even bigger. -Conclusions: -we could quote an omega-gamma if we insisted on a Gamma in the range of 10-12 (instead of 7) but with a target thickness of ~15keV/u we can't discriminate Gamma well -There is one key aspect where we are better than TUDA and that is we have a better idea of the energy spread. Our disadvantage is needing to relate runs at different beam energies. 6) Joel presented images to be included in the minutes but to be talked about in more detail next week. -TUDA uses different energy scale than DRAGON -postulated that the prague magnet calibration may have changed between runs. -if we want to compare with TUDA we should use same energy scale. -The discussion will be continued next week... 7) General discussion: -We don't understand the performance at thicker reasonances (though omega-gamma about the same regardless) and we should do a broad reasonance with stable beam. -TUDA gets broad reasonances right. They had one week of stable beam and measured two reasonances (~700 and ~1300/1400) and found energy and width as found i litterature. -Stable reasonances should be published to prove that DRAGON works.