Primary Collimator Live Page
Tony's Status Report
Klaus's Status Report
Michael's Web Page
Qweak Simulation Forum
Keep Out Zones a la Allena
Previous Reports
Virginia Tech Update for Tracking Group,
At the collaboration meeting we had some preliminary results which indicated backround rates and powers in the plugs that seemed intolerably high. Since then we have devoted a lot of effort to properly understanding the generation of electromagnetic background at small angles. There are lots of subtleties and chances for over-counting - we want to make sure we are getting it right.
Right now we are considering an extremely simplified geometry (nothing but a target and a far downstream detector) and we are looking at particles in the approximate angular range subtended by the first plug. One clue to part of the problem is shown in Figure 1. At low angles, the cross section starts to blow up, but because of multiple scattering effects, some of those low angle events are able to make it into the acceptance of our plug. The "dip" occurs because of the competing effects of the bulk of events being generated in that angular range, and the rapidly increasing cross section. Integrating the black curve yields a rate larger than the incident particle rate.
|
|
Figure 1 - A plot of theta_o for all elastic ep particles (black) and for those "hitting the plug" (green). |
The majority of the overcounting is due to the fact that to properly estimate rates, the calculation assumes that once the particle interacts it is removed from the beam. In our extended target, the low angle events have a non-zero probability of interacting multiple times - but in our rate estimate we are counting each interaction as a separate particle.
We could also overcount because we are considering "showers", eps, and mollers (and inelastics?) separately. We could also overcount when trying to properly include radiative processes - the shower reaction yields 2X what the point target estimate suggests.
Some preliminary results:
The rate at the region 3 detector is down to 9%, with concrete wall, in a
simulation we have some trust in, and using Neven's parameterization.
We are working on details.
Power deposited in the first plug:
At least: 650 W
Not more than: 5000 W ?
Our half-chamber prototype is assembled and gas is flowing (Figure 2). We have powered three of the eleven Nanometrics amplifier cards and are seeing oscillations on the fast OR outputs.
We have tried a variety of grounding connections (Figure 3 and 4).
The oscillations vary (see Figures 5 thru 7). We can get it to stop oscillating (Figure 8) but it is not stable. It is definitely affected by the ground connection.
Work continues to establish a good ground and stable (strain relieved) card connections.
|
|
|
|
Figure 2 - View of the new prototype setup.
|
Figure 3 - Grounding the card...
|
Figure 4 - ...to the aluminum cage around |
|
|
|
Figure 5 - 13 MHz high frequency noise.
|
Figure 6 - 51 MHz high frequency noise.
|
|
|
|
Figure 7 - 21 MHz high frequency noise.
|
Figure 8 - No high frequency noise!
|
