The figure on the left shows the Moller electrons without the minitorus. They are swept away by the main magnet after the middle chamber location. The rate at the middle chamber location is approximately 1200 kHz/nA. The figure on the right shows the Moller electrons with the minitorus in place (MFIL=-.049). They are swept toward the beamline and into the secondary collimator. The rate at the middle chamber location is approximately 36 kHz/nA.
Figure 1
The leftmost plot is of the weighted rates of the eps and mollers vs. radial distance for the minitorus off. The ep rate is multiplied by a factor of 100. The middle plot is of the weighted rates of the eps and mollers vs. radial distance for the minitorus bending down (current density ~610 A/cm^2). The ep rate is multiplied by a factor of 40. The last plot is of the weighted rates of the eps and mollers vs. radial distance for the minitorus bending up (current density ~610 A/cm^2). The ep rate is multiplied by a factor of 100. It looks like if we lowered the top collimator opening by 6 cm, we would take advantage of this separation. The ep rate is much lower at the top (though the assymmetry is bigger). However, this is for a very large current density. The desired current density is ~470 A/cm^2.
Figure 2
These plots show the ep/moller separation for our nominal current density at a detector before the secondary collimator. The plot on the left is for bending down, the one on the right is for bending up. The largest part of the moller rate is not bent out of the secondary collimator opening if we bend up.
Figure 3
Can we do it? (On the left): Minitorus at our current density, lowest radial position and longest lever arm.
Best Try (On the right): Minitorus at highest current density, lowest radial position and longest lever arm.
Still not good enough?
Figure 4
The top plot shows the moller rate as a function of radius and the bottom one shows moller energy as a function of radius for a current density of ~470 A/cm^2, bending down. The plots on the left are for before the secondary collimator, the ones on the right are for after the secondary collimator.
Figure 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
----
Table 1
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 6
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 7
The plot on the left shows the bend angle of the ep elastics due to the minitorus bending down as a function of current density. At our ideal current density of 470 A/cm^2, the bend angle is approximately .31 degrees. The plot on the right shows the bend angle of the ep elastics due to the minitorus bending up as a function of current density. At our ideal current density of 470 A/cm^2, the bend angle is approximately .31 degrees.
Figure 8
The plot on the left shows the moller rates as a function of current density if we bend the mollers toward the beampipe. The plot on the right shows the moller rates as a function of current density if we bend the mollers away from the beampipe.
Figure 9
This plot shows the mean x values as a funtion of y in y bins of 10 cm, and shows mean y values as a function of x in x bins of 2 cm. This is superimposed over a watermark picture of the ep-peak distribution with the minitorus off. The values for minitorus off are black, and those with the minitorus on and the primary collimator shifted up by 1 cm are red.
Figure 10
The top plot is the ep peak distribution at the main detectors for the "original" primary collimator, no secondary collimator, minitorus off (but still there). The middle plot is the ep peak distribution at the main detectors for the "original" primary collimator, no secondary collimator, minitorus current density ~470 A/cm^2. The bottom plot is the ep peak distribution at the main detectors for the primary collimator shifted up by 1 cm, no secondary collimator, minitorus current density ~470 A/cm^2.
Figure 11
The leftmost plot is the ep peak distribution at the middle chambers for the "original" primary collimator, no secondary collimator, minitorus off (but still there). The middle plot is the ep peak distribution at the middle chambers for the "original" primary collimator, no secondary collimator, minitorus current density ~470 A/cm^2. The rightmost plot is the ep peak distribution at the middle chambers for the primary collimator shifted up by 1 cm, no secondary collimator, minitorus current density ~470 A/cm^2.
Figure 12
This is a solidworks image of the minitorus coils.
Figure 13
This is a solidworks image of the minitorus coils with the primary and secondary collimators.
Figure 14
This figure shows the magnetic field (kG) as a function of radial distance (cm) for a current density of ~470 A/cm^2. The profile is shown at the entrance, center and exit of the minitorus. The envelope of the mollers is shown at the entrance (blue) and exit (pink or green) of the minitorus for bending up (green) and bending down (pink). The ep envelope is blue.
Figure 15
Circular Minitorus
These plots show the values of the B field varying with R, phi and Z respectively, while holding the others constant, for the circular minitorus with a current density of ~470 A/cm^2.The following plot shows a magnetic vector field for chosen points at the center of the circular minitorus, with the B field scaled up by 10 in order to see the vectors. The z-component of the field is not used.
Figure 16
