Minutes of the DRAGON group meeting January 8, 2008present CR, DO, DH, CD, LB, PB, UH (rec) * status of DRAGON - EDs have been restored - sections with mass and charge slit boxes are pumped down - ion pump: to be investigated * Quad alignment - current transmission: 86% between charge slits and final slits - GEANT simulations needed (UH) - the report from the quad movement so far is attached - lowering the quads is relatively easy and reliable (using dial gauges) - DH, DO, UH will lower Q1 still further on Wednesday * EEC report - EEC report draft below - Ne19 will have to be resubmitted - Mg23 should be run this year * upgrade - the drawings were put into the machine shop on Dec 12th - the parts will be ready earliest mid-February, propably in March - the Total Station might be used for alignment - necessary purchases: + turbo pump: PM looks into that + SHV feedthroughs for MCPs * DAQ - the DAQ group has asked whether Dragon wants them to buy anything - they already give us ADCs and TDCs - a VME crate is needed -----EEC report draft----- INTRODUCTION The TRIUMF Subatomic Experiments Evaluation Committee met Monday December 10 to Wednesday December 12, 2007. The Committee considered 6 new proposals and 4 progress reports. There were reports from the Beam Strategy Group and on ion source development. TRIUMF has instituted a two-tier experiment approval system for ISAC experiments. The first step is Stage-1 where the physics is judged but shifts are not allocated either because the beams are not currently available or the apparatus is not ready. Once the apparatus is ready and the beam is available, Stage-2 approval can be requested and, if approved, shifts assigned. Stage-1 priority ratings are used to set beam development and TRIUMF resource priorities. The change to a two-tier process necessitated a review of the entire ISAC subatomic physics program. Written updates were submitted on many individual experiments awaiting beam, and group reports were received for the major facilities where the outstanding proposals were ranked by both scientific interest and feasibility. The Committee recognizes the effort and time that went into preparing these reports. They were invaluable to the Committee for the initial sorting of the proposals into Stage-1 or Stage-2. The recommendations on the approval level of individual experiments are given in the reports on each group presentation. It is recommended that each group maintain a rolling list of its priorities to assist TRIUMF in allocating beam time and setting development priorities. The scientific output of ISAC continues to be limited by the lack of available beam time and the need for a more diverse array of beams. Beam development is very demanding, and the Committee recommends that TRIUMF put more resources into ensuring that new beams are developed in a timely fashion. The Committee applauds the addition of a person to target development but remains concerned that the manpower and time devoted to beam and target development is far from optimal. There is also a clear need for post-mortem analyses of targets at the end of their use. Additional production targets, such as those envisioned for the next five-year plan, would significantly increase TRIUMF's scientific output and better utilize the impressive array of experimental apparatus that is currently available and being developed. As an aid to users and the committee, TRIUMF should make available on its web site a continuously updated list of available beams and their expected intensities. This information is necessary in order to decide when it is appropriate for an experiment to move to Stage-2 approval. ********************************************************************* Report on DRAGON The DRAGON facility is unique in offering the capability to perform direct measurements of reactions of astrophysical importance that involve radioactive nuclei at low bombarding energies. The past studies by the group of the proton captures on 21Na and 26Al are textbook examples of how such measurements should be performed. Since capture reactions generally have small cross sections, the required radioactive ion beam intensities needed to measure them are high. Consequently, beam development to obtain sufficient intensities for capture measurements is very demanding. As a result, the beam intensities are presently not available at TRIUMF to reach the physics goals in the relatively large number of well-motivated proposals from the DRAGON group. The group lists 14 proposed measurements in their \u201cFeasibility Priority List,\u201d which represents a compromise between science motivation and beam availability. Their top four priorities for Stage-2 approval involve proton captures on 22Na, 33S, 23Mg and 19Ne. A measurement of the first three of these reactions over the next few years (together with the 18F(p,?) measurement at TUDA) will provide a nearly complete set of experimentally determined reaction rates for modeling classical novae, thus making novae the only thermonuclear explosions in the universe for which the nuclear physics input will be mainly based on experiment. With the nuclear physics input on a solid foundation, other crucial but poorly understood stellar model properties, such as accretion, convection and mass loss, can be explored in a far more meaningful way. The expected advances in nova modeling will not only improve our understanding of the actual observations (that is, nova light curves and shell abundances), but may also shed light on the inner workings of more complicated explosions, such as supernovae and X ray bursts. There are four more reaction measurements that are required to base current nova stellar models entirely on direct low-energy measurements. These are the measurements of the proton captures on 25Al, 30P, 17F and 13N. They have been listed by the DRAGON group in the lower half of their \u201cFeasibility Priority List\u201d since these beams are not available. The Committee recommends that the beam development group makes the production of these beams a high priority. With few exceptions, the Committee generally concurs with the assessment of the DRAGON group on their physics priority list. Below we comment briefly on each reaction given in the list: S1027 (22Na+p): important for predicting the 1275 keV gamma-ray flux from novae; the implantation of a radioactive target will be performed at TRIUMF, while the actual capture experiment is scheduled to take place at the University of Washington; 4 shifts at high priority have been approved to make the target. S1122 (33S+p): important for future identification of candidate nova presolar grains; requires new supernanogan ion source; 8 shifts at medium priority have been approved. S810 (23Mg+p): influences nova abundances in the A=20-30 range; although ranked by the DRAGON group rather low in their "Science Priority" list, we regard a direct measurement as a crucial step forward to better understand nova models; 33 shifts at high priority have been approved. S811 (19Ne+p): this reaction is part of the 15O(?,?) 19Ne(p,?) breakout sequence in X-ray burst models; according to the DRAGON group, a proper study would require an intensity in access of 108/s, while the intensity projected by the beam development group amounts only to 107/s. In view of the large overall beam time demand, we feel that the currently achieved 19Ne intensity should be improved significantly before we can approve the experiment. Because several years have passed since the original proposal was submitted, we ask the spokespersons to submit a new proposal to the EEC; this also gives the group the opportunity to strengthen the astrophysical motivation of the proposed measurement, that is, by seeking theory support to explore the sensitivity of X-ray burst models to variations in this reaction rate. (The differences in the energy generation shown during the presentation were obtained by dividing the 19Ne+p rate by a factor of 1000, although the same slide states a rate uncertainty of 1-2 orders of magnitude.) S1123 (18F(p,?)): competing reaction to 18F(p,?) in novae; a radioactive beam of sufficient intensity for a significant measurement is currently not available; no change to previous assessment; Stage-1 approval; medium-high science priority. S1076 (17O(p,?)): important in nova nucleosynthesis; after a recent revision of literature data, the two independently measured strengths of the 190 keV resonance are now in better agreement; thus the EEC sees no compelling reason to pursue this measurement at DRAGON; we consider this proposal closed until it can be demonstrated that the remaining (relatively small) discrepancy of the data has an important effect on nova observables. S946 (17F+p): important for 511 keV gamma-ray flux in novae; the reaction has not been measured directly yet, but the rate is currently based on relatively reliable nuclear structure information; according to recent nova models the remaining uncertainty in this rate has a smaller effect on the nucleosynthesis compared to some other reactions; a radioactive beam of sufficient intensity for a significant measurement is currently not available; Stage-1 approval; medium-high science priority (revised from previous assigned priority). S1125 (25Mg+p). At the time when the original proposal was submitted, the large difference obtained for the strength of the 198 keV resonance measured with the in-beam technique and with AMS warranted another, independent, measurement. However, the recent study by the LUNA collaboration has ruled out the AMS result and thus there is less motivation for a DRAGON measurement. We consider this proposal closed until it can be demonstrated that a new (fourth) measurement is of crucial importance. S983 (11C+p): important for models of massive, low-metallicity stars; a radioactive beam of sufficient intensity for a significant measurement is currently not available; no change to previous assessment; Stage-1 approval; medium-high science priority. S989+990 (26gAl+p, 26mAl+p): important for galactic 26Al production; phase I (26gAl+p) has been completed, while a radioactive beam of sufficient intensity for a significant measurement is currently not available for phase II (26mAl+p); it is not obvious how sensitive current massive star models are to variations in the reaction rate from the meta-stable state; because several years have passed since the original proposal was submitted (and new nuclear structure information may have recently become available), we ask the spokespersons to submit a new proposal for both the DRAGON and the TUDA measurement to the EEC; this also gives the group the opportunity to strengthen the astrophysical motivation of the proposed measurements, that is, by seeking theory support to explore the sensitivity of 26Al production in massive stars to variations in this reaction rate. S922 (25Al+p): important for a possible contribution of novae to galactic 26Al production; a radioactive beam of sufficient intensity for a significant measurement is currently not available; Stage-1 approval; high science priority. S805 (13N+p): important for nova nucleosynthesis; the resonance strength for the reaction has been measured directly before and the reaction rate is also constrained by reliable nuclear structure information; a DRAGON measurement would be important to check the previous direct measurement and to verify the sign of interfering cross section amplitudes; a radioactive beam of sufficient intensity for a significant measurement is currently not available; Stage-1 approval; medium-high science priority. S1108 (30P+p): strongly influences nova nucleosynthesis above A=30; a radioactive beam of sufficient intensity for a significant measurement is currently not available; Stage-1 approval; high science priority. S813 (15O+?): important for initiation of breakout from hot CNO cycles in x-ray burst models; a radioactive beam of sufficient intensity for a significant measurement is currently not available; Stage-1 approval; high science priority. -----EEC report draft-----