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Youngguang's Status Report
OU's Status Report
Dilution factor notes (Dave Bowman)
Previous Reports
Virginia Tech Update
for Tracking Group,
Chambers Update:
Ertalyte arrived. Jobs have been submitted to the shop to make 7 frames to make a single wire plane prototype.
Quote for .5 mil Mylar with 1000 angstroms of Aluminum on both sides from Sheldahl - 48'' wide is $3.70/ft. 4 week delivery - it's been ordered.
Copper clad mylar too expensive.
Minitorus recap:
using the minitorus to bend the mollers away from the beamline won't work
Bending the mollers toward the beampipe also shifts the ep peak by approximately 2 cm downward (actually 1.7 cm)
Solution: Increase the mean scattering angle by the amount the ep's are being bent downward, ie. ~.4 degrees
So...
With our current nominal setup we have minitorus bending mollers toward the beampipe with a
current density of ~470 A/cm^2, 10 cm from beamline center, with a 1 cm shifted primary
collimator and a modified ~4'' Pb secondary collimator
mollers suppressed to 20 kHz/nA
with extended target simulation FOM approximately the same (Table 1)
at entrance to main magnet, clearance is now 2 cm more than before (Figure 1)
similar shape and focus (Figures 2-5)
Figure of Merit table with Rate and mean Q2 from GEANT simulation. The FOM stays approximately constant with a 1 cm shift.
Primary Collimator Shift (cm)
Rate (MHz)
Mean Q2
FOM = R
Hadronic Contibution
0.0
627
.0268
.4503
31%
1.0
535
.0294
.4624
33%
2.0
434
.0322
.4500
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Table 1
We looked into Roger's question about the mean Q2 and rate for a lower beam energy (Table 2)
Beam Energy (GeV)
Primary Collimator Shift (cm)
Rate (MHz)
Mean Q2
FOM = R
Hadronic Contibution
1.065
0.0
836
.0224
.4197
27%
1.065
1.0
706
.0247
.4299
29%
1.015
0.0
921
.0203
.3809
25%
1.015
1.0
785
.0225
.3560
27%
Table 2
These plots show the ep peak at the entrance to the main magnet for no minitorus, minitorus on and minitorus on with a shifted primary collimator. The mean Q2 and rate with the primary collimator shifted is listed in the table above. It appears that changing the mean angle of the experiment will actually give us more breathing room than before.
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Figure 1
These plots show the ep epeak distribution at the main detectors for no minitorus and for the minitorus and the shifted primary collimator. At least by eye it looks like there is no significant change in the distribution.
Figure 2
This plot shows mean x values in 10 cm bins of y and mean y values in 2 cm bins of x, overlayed on a plot of the ep peak distribution at the main detectors. The plot indicates that the mean is shifted downward, but increasing the main magnet field should compensate for this.
Figure 3
This plot addresses the issues of mean position and shape of the eps at the cerenkov bar location. In our simulation, detectors 11-16 are spaced 25cm apart in z, and detector 14 (blue) is located at z = 530cm. For each detector location, the mean position in x was calculated in 10cm bins of y. The triangles are for no minitorus, with the "original" primary collimator. The squares are for the minitorus on with a primary collimator shifted 1cm away from the beamline. The mean position shifts by 2 cm, but the shape is the same for detectors 14-16. It changes slightly for detectors 11-13.
Figure 4
These two plots address the issue of focus at the cerenkov bar location. Again, in our simulation, detectors 11-16 are spaced 25cm apart in z, and detector 14 (blue) is located at z = 530cm. For each detector location, the sigma in x was calculated in 10cm bins of y. The plot on the left shows the focus for the minitorus off and original primary collimator. The plot on the right shows minitorus on and shifted primary collimator.
Figure 5
There are low energy electrons which seem to have lost energy after going through the main magnet and still make it into the acceptance of the cerenkov bar (Figure 6, left). These electrons come from the target, but have energies as low as 200 MeV. They account for ~2% of the total rate at the cerenkov bar. When we change the global volume from air (left) to vacuum (right) these low energy electrons disappear. It seems that they are the result of bremsstrahlung in the air after the main magnet. We are not sure of the effect of the low energy eps on our Q2 measurement.
Figure 6
Future plans:
We want to do a crude estimate of the effect of the low energy eps on our Q2 measurement
Further work includes checking that we are able to run with minitorus on and off, possibly changing the main torus field
We may only need to shift the primary collimator by .5 cm, but...
to be sure that the minitorus is not hitting the main magnet support we need the dimensions and position of the bar that
is causing all of the trouble so we can check the rates on the bar
