Dragon Group meeting Feb. 19th 2002 Minutes Present: PM, DO, DH, MC, LB, AO, SB, SE, CW (recorder), AC, CJ SE Presented Results of Feb Runs A better 'new' tune was acquired from wobbler studies: Q1 Q1 + 10% SX4 on Q9 ~ Q10 The 20Ne(p,g) reaction at 1160.9 keV/u confirmed the energy calibration at MD1 obtained from 21Ne(p,g) at 270.0 keV/u. Results were E/A=const*(Bq/m)^2, with const=(4.824 +/- 0.003)*10^-4. The yield of 20Ne(p,g) at 1160.9 KeV/u was measured to be (6.8 +/- 1.4) singles/sec*pnA. This may be compared with a value expected from the literature of (10.0 +/- 0.7) singles/sec*pnA. Delta-E was found to agree with SRIM to within 11%. AO pointed out that the SRIM value entered into the determination of target effective length; SE said that there had been independent confirmation of SRIM from observation of resonance z-shift in the central cell; DH questioned whether the z-mask scale was known well enough to validate the SRIM value. The resonance was measured to be at 1158.25 keV/u; discrepancy from the expected value may be due to an asymmetric target profile. DH suggested that there may be sufficent data from the 15N(p,alpha) runs to obtain a more reliable target profile since this is a narrow resonace. A profile of the BGO efficiency at 3.5 MeVwas presented based on the coincidence/singles ratio vs. beam energy. See attachment. Results of 21Ne at 270 keV/u on He target showed that there was no background due to chemical reactions of the type Ne + H2 -> NeH + H. The measurements of 21Ne(p,g) at 270 keV/u were repeated to compare with runs from Dec. 6th, 2001. Results were consistent which suggests that there has been no change in the setup from last year. Transmission of DRAGON was tested through the slits with the 'old' tune and showed no sign that low-energy 22Mg recoils were being lost in the Nov/Dec runs with MX slits at 15mm opening. It was found that leaky beam could be suppressed 10-fold by closing the MX, FX and FY slits to 15mm without reducing the coincidence rate by more than 4%. The MCP was found to have poor efficiency and requires further testing with a beta source. AO suggested that the MCP could be baked with halogen bulbs in vacuum. Results from the 24Mg(p,g) at 817 keV/u reaction were presented. The measured yield was (1.27 +/- 0.27) singles/sec*pnA. This was about half the value expected from a compilation but the compilation value was the result of renormalizing earlier data upwards 30%, not a direct measurement. It was calculated that the error due to slit positions or a thin target was 14% at most. Omega*gamma was measured to be 320 meV. There was a high probability for coincidence events due to a low threshold in the gamma array and gamma cascades at lower energies. A thorough GEANT computer simulation incorporating these cascades is needed. DH Presented his Joblist The joblist was e-mailed to DRAGON group members yesterday. Add to the joblist: -cryo temperature calibration -Ion pumps -new version of RedHat will be installed (Pierre Amadrus). -conditioning of dipoles (Miguel) -water shutdown Wednesday Feb 20th -SB suggested an alarm system in the event that anything trips off (Peter Green). -SE suggested a system to ensure that either FCF or FCM is in when one ought to be. -need a system in place to ensure that the MCP and FCF do not interfere with eachother (Hart). -the MCP chamber must be vented carefully because of foils! 6 weeks until we should be ready to run again 3) SB Presented his analysis of 21Na(p,g) An analysis of the yield done independently of that by JR was presented. Results were similar. Error bars need work because of low (Poisson) statistics. See attachment. 4) Miscellaneous -Deadline: March 1st to decide what is to be done with beamtime in 6 weeks and for written material from LB/SE/AC for the 822 keV resonance in 22Mg. -It was debated whether any of the April beamtime should be spent on the 822 keV resonance. DH suggested that a measurement on the low-energy side may be helpful in pinning down the width Gamma; LB and SE suggested that more data points around the maximum yield should be taken. If any time is spent on this resonance, it should be strictly limited and with a goal of making a big reduction in uncertainty in omega-gamma. -DH: Main goal for April/May beamtime should be: Firm up low energy resonance and go after the other resonances which were not looked at during Nov/Dec running.