Meeting minutes Tuesday 27th May 2003

Present:  AB, AO, CG (scribe), CJ, CR, CW, DG, DH, DO, JDA, JR, LB, MA, ML, 
PM, ZL 

First we would like to welcome Anthony Olivieri to our group for the summer 
from McMaster University.

1.  Last week's minutes are not available.  MA's hard drive, on which the 
minutes were stored, crashed.  MA has a hardcopy, and will reproduce the 
minutes.  

2.  Acceptance/wobbler discussion
JD:  Something is clipping off part of the recoil.  Acceptance should be 
uniform within a cone, but the wobbler studies show that it is not.  LB 
notes that the beam line is moved by as much as one centimeter.  DH 
suggests locking out MD1, taking off the port, and looking for a 
disruptance.  LB asks why the old wobbler results differ from the new, and 
DH says that for the new, a bigger aperture was installed in the pumping 
stage.  LB thinks this should be mentioned in the paper.  DH: we learned 
that we should have paid more attention to beam divergence.  JD:  The 
wobbler studies will be redone.  

3.  ECR discussion
LB attended an ECR meeting on Wednesday.  JD: The ECR is an ion source.  
TYSOL had one running for 10 years; this new one, of different design, has 
yields up to a factor of 100 too low.  More testing is underway.  

4.  12C(a,g)16O 
JR shows histograms produced for 1070keV/u data, including an angular 
distribution histogram.  He describes the method for extracting events from 
.mid files, and the calculation used to obtain gamma ray angles.  Note that 
HLE means 'heavy ion time - leading edge time' - and this is used in order 
to remove detector to detector variations. DH suggests an additional 
correction for the computed flight distance. JR notes that the slope in 
the cgo HLE time x cgo cos(theta) is a consequence of momentum conservation. 
He shows angular distribution histograms for the left and right sides of 
the gamma detector, noting that detectors 1-10 were included in each 
histogram. The purpose of these is to identify a signature for acceptance 
loss. He expects full acceptance above some unknown threshold energy.  At 
1070keV/u, no obvious signature is seen.  He then shows histograms for 
900keV/u, in which a hint of asymmetry is seen in the left and right 
angular distributions (attachment 1). 

JR then shows a plot of Lrf vs beam energy.  During long runs the beam 
energy is seen to jump around much more than it should.  Stripper foil 
changes do not seem to explain these shifts, but to make sure of this JR 
suggests retarting runs and measuring beam energy after every stripper 
change (attachment 1).

ZL discusses simulation in which the two peaks in the cH-energy histogram 
[discussed last week] are reproduced.  JD suggests that ZL include angular 
distributions and leave out cascades in the simulation (attachment 2).

5. 13C(p,g)14N 
CR discusses Monte Carlo of 13C(p,g)14N.  His purpose is to explain the 
double peak in the cH-energy histogram.  The histogram 'Distribution of 
recoil angles' shows that most events occur at 20mrad, and CR concludes 
that the double peak occurs because acceptance issues cause these events to 
be lopped off. (attachment 3).

ML continues discussion of acceptance issues.  He shows plots of 
'x-projection vs anodesum' for opposing gamma detectors.   Detectors on the 
right (as the beam sees) have much broader peaks.  Broad peaks are desired.
(attachment 4).

6.  Conclusions
AB will give his presentation next week.  LB mentions germanium detectors 
and a grant request.  DH requests summaries of work done from ZL, CR, ML, 
and JR.  Another meeting is proposed to discuss acceptance problems