UVA chambers HKS chambers VT prototype chamber GARFIELD Simulations VT Qweak elog
- 33 -
?-?-2006
- 32 -
7-19-2006
See rows 23, 16, 18, 27
We want the E-field to be no smaller than 600V/cm between the field and sense wires (row 27, Figure 2). The ratio of the cathode to field wire voltages (row 23) can tell us the approximate value of Emin. Row 18 shows examples of potential surfaces for different cases, and there can actually be a potential well for the electrons at the field wire as well as the sense wire. Row 16 shows tracks on the right and left with wells at the field wires. The middle case has a slight hill.
Figure 1 - Plot of Ex for the (-1300_-2000) case.
Figure 2 - Plot of Ex for the (-1500_-1800) case.
- 31 -
7-19-2006
Figure 1 - (-1500_-2000) case with no air contamination, adjacent cells.
Figure 2 - (-1500_-2000) case with no air contamination, one cell.
- 30 -
7-17-2006
Figure 1 - Data with more (top) or less (bottom) air contamination (one hit).
Figure 2 - Sim with more (top) or less (bottom) air contamination (one cell).
Figure 3 - Data with more (top) or less (bottom) air contamination (no cuts).
Figure 4 - Sim with more (top) or less (bottom) air contamination (adj. cell).
- 29 -
7-13-2006
Figure 1 - (-1500_-2200) case (red markers), data run 193 (black line) with one hit (and one cell).
Figure 2 - (-1500_-2200) case (red markers), data run 193 (black line) with more than one hit (or one cell).
- 28 -
7-13-2006
It looks like air contamination may be able to explain our data. These plots compare a GARFIELD simulation with 10% air contamination with tracks originating only in one cell (Figure 1) and one with tracks originating also in the two adjacent cells. Figure 2 shows a drift time distribution from a data run with the same voltage settings and requiring only one hit per event. The data and the simulation for one cell with air contamination seem to match very well!
Figure 1 - (-1500_-2200) case, with +/- 30 ° in one cell, with 10% air contamination.
Figure 2 - (-1500_-2200) case, data run 193.
Figure 3 - (-1500_-2200) case, with +/- 30 ° in adjacent cells, with 10% air contamination.
- 27 -
7-12-2006
Figure 1 - Mixture of 20% Ar - 80% ethane.
Figure 2 - Mixture of 90% Ar - 20% CO2.
Figure 3 - Mixture of 90% our gas (88% Ar - 10% CO2 - 2% methane)
and 10% air (78% N2 - 21% O2 - 1% H2O).
- 26 -
7-11-2006
Figure 1 - (-1500_-2200) case, with +/- 30 ° in one cell.
Figure 2 - (-1200_-2200) case, with +/- 30 ° in one cell.
Figure 3 - (-1500_-2200) case, data run 193.
Figure 4 - (-1200_-2200) case, data run 199 .
Figure 5 - (-1500_-2200) case with +/- 30 ° .
Figure 6 - (-1200_-2200) case with +/- 30 ° .
25
Figure 1 - Some arrival time distributions from the chamber for various wires.
24
These two plots compare the arrival time distributions of the (-1500_-2200) case for tracks in the two adjacent cells with tracks only in the cell of interest. It appears that the long time tail is due to tracks that probably would make a hit in an adjacent cell, probably at an earlier time.
Figure 1 - Arrival times of tracks including two adjacent cells.
Figure 2 - Arrival times of tracks in the cell of interest.
23
This plot shows the variation of the minimum E field between the field and sense wires on the x-axis with the ratio of the field and cathode voltages. Note that they don't follow exactly the same line, but roughly speaking, the ratio could be used to guide us to the minimum field wire potential for a given cathode potential. Row 22 shows plots of the potential along the x-axis for (-1400_-2200) and (-1500_-2200). Somewhere between those two voltages, the well becomes a hill.
Figure 1 - Plot of minimum E field on x axis vs. ratio of cathode to field voltages.
22
These plots show -V along the x-axis. The case with (-1400_-2200) shows a small "well" at the field wire location while the (-1500_-2200) case shows a small hill. The "transition potential" must be somewhere between -1400 and -1500 V. The minimum E field in the (-1500_-2200) goes down to .4 kV/cm, and becomes zero in the case of (-1400_-2200). Our drift velocity vs. E field plot (see row 9, Figure 1) suggests that we would like the E field to be between ~600 V and 10kV. Outside of this range and the drift velocity is no longer approximately constant with the E field.
Figure 1 - -V along x-axis for the (-1400_-2200) case.
Figure 2 - -V along x-axis for the (-1500_-2200) case.
21
These tracks both crossed the x-axis at -.349cm or -.116cm, but the ones on the left were at 7 degrees and the ones on the right wer vertical. The x-axis should be multiplied by 10-3. There doesn't seem to be a significant difference in the timing of the arrival of the first electron in this angular range.
Figure 1 - Arrival time distribution for a 7° track at x=-.349cm.
Figure 2 - Arrival time distribution for a 0° track at x=-.349cm.
Figure 3 - Arrival time distribution for a 7° track at x=-.116cm.
Figure 4 - Arrival time distribution for a 0° track at x=-.116cm.
20
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19
These plots of Ex along the x-axis clearly show that for the (-1400_-2200) and the (-1000_-2450) cases the field wires as well as the sense wires have wells, while for the other two cases (-1500_-2200) and (-1400_-1400) there are wells for the electrons only at the sense wires.
Figure 1 - x-component of the electric field along x-axis (-1400_-2200).
Figure 2 - x-component of the electric field along x-axis (-1500_-2200).
Figure 3 - x-component of the electric field along x-axis (-1000_-2450).
Figure 4 - x-component of the electric field along x-axis (-1400_-1400).
18
The plots show the potential surfaces for the new protype with three different field and cathode settings. With the field and cathode set to the same voltage (Figure 3) the field wires have obvious peaks. With the cathode potential much larger than the field wire potential, it seems that there are wells at the field wires as well as at the sense wires (Figure 2). Although it is not as obvious, I believe there may even be wells at the sense wires in the case of (-1400_-2200) based on the tracks shown in row 16 Figure 1.
Figure 1 - Plot of surface of -V for -1400_-2200.
Figure 2 - Plot of surface of -V for -1000_-2450
Figure 3 - Plot of surface of -V for -1400_-1400.
17
Figure 1 - Arrival time distribution for e- from tracks in
Figure 2 - Arrival time distribution for e- from tracks in the
Figure 3 - Arrival time distribution for e- from tracks in
Figure 4 - Track in the upper left region (-1400_-1400).
the middle of the cell (1400-1400).
upper left corner of the cell (1400-1400).
between the S and F wires (1400-1400).
16
The arrival time distribution for the (-1000_-2450) case is missing; is this possibly because all of the first electrons were going to the field wire instead of the sense wire? You can see in the potential surface plot above that there are two wells for that potential "geometry".
Figure 1 - Track in the upper left region (-1400_-2200).
Figure 2 - Track in the upper left region (-1500_-2200).
Figure 3 - Track in the upper left region (-1000_-2450).
15
Figure 1a - Arrival time distribution for e- from tracks in
Figure 2a - Arrival time distribution for e- from tracks in
Figure 3a - Arrival time distribution for e- from tracks in
Figure 1b - Arrival time distribution for e- from tracks in
Figure 2b - Arrival time distribution for e- from tracks in
Figure 3b - Arrival time distribution for e- from tracks in
Figure 1c - Arrival time distribution for e- from tracks in the
Figure 2c - Arrival time distribution for e- from tracks in the
Figure 3c - Arrival time distribution for e- from tracks in the
the middle of the cell (1400-2200).
the middleof the cell (1500-2200).
the middle of the cell (1000-2450).
between S and F wires (1400-2200).
between S and F wires (1500-2200).
between S and F wires (1000-2450).
upper left corner of the cell (1400-2200).
upper left corner of the cell (1500-2200).
upper left corner of the cell (1000-2450).
14
For these plots, the x-axis was parameterized as 3*t-1.5, where 0< t<1.
Figure 1 - Plot of E field along x-axis for -1400_-2200.
Figure 2 - Plot of E field along x-axis for -1500_-2200.
Figure 3 - Plot of E field along x-axis for -1000_-2450.
13
Figure 1 - Frame and board from adjacent octant.
Dose on Frame >1 rad/nA/hr
Dose on Electronics >1 rad/nA/hr
12
Figure 1a - Isochrones for 1400-2200 2% methane.
Figure 2a - Isochrones for 1500-2200 2% methane.
Figure 3a - Isochrones for 1000-2450 2% methane.
Figure 1b - Contours of V for 1400-2200 2% methane.
Figure 2b - Contours of V for 1500-2200 2% methane.
Figure 3b - Contours of V for 1000-2450 2% methane.
Figure 1c - Arrival times for 1400-2200 2% methane.
Figure 2c - Arrival times for 1500-2200 2% methane.
Figure 3c - Arrival times for 1000-2450 2% methane.
11
Figure 1a - More realistic track near field wire.
Figure 2a - More realistic track near sense wire.
10
Figure 1a - Scintillator TDC spectra.
Figure 2a - Data for prototype II long run (nsec).
Figure 3a - Sim for prototype II high stat (&mu sec).
9
Figure 1a - Drift velocity vs. E for the Mainz cell in our gas
Figure 2a - Drift velocity vs. E for the Mainz cell in their gas
Figure 3a - Arrival times for the Mainz cell in their gas
(sense wires at 3000V).
(sense wires at 3000V).
(sense wires at 3000V).
8
Figure 1a - Counters of V for the Mainz cell in our gas
Figure 2a - Isochrones for the Mainz cell in our gas
Figure 3a - Arrival times for the Mainz cell in our gas
(sense wires at 3000V).
(sense wires at 3000V).
(sense wires at 3000V).
7
Chamber |
Field |
Cathode |
wire spacing |
cathode spacing |
mean arrival time |
max arrival time |
Hermes forward |
-1550 |
-1410 |
7 |
8 |
.036 |
.07 |
Hermes back |
-1770 |
-1770 |
15 |
16 |
.089 |
.15 |
Prototype I |
-1800 |
-1800 |
12.2 |
19.05 |
.075 |
.12 |
Prototype II |
-1800 |
-1800 |
9.3 |
19.05 |
.058 |
.09 |
Mainz chamber |
0 |
0 |
20 |
20 |
.109 |
.2 |
6
Figure 1a - Contours of V for the old prototype (-1800 C, -1800 F).
Figure 2a - Contours of V for the new prototype (-1800 C, -1800 F).
Figure 3a - Contours of V for the Hermes geometry (-1410 C, -1550 F).
Figure 1b - Drift lines of a 45 degree track for the old prototype.
Figure 2b - Drift lines of a 45 degree track for the new prototype.
Figure 3b - Drift lines of a 45 degree track for the Hermes geometry.
Figure 1c - Drift lines (yellow) and isochrones (green) for the old prototype.
Figure 2c - Drift lines (yellow) and isochrones (green) for the new prototype.
Figure 3c - Drift lines (yellow) and isochrones (green) for the Hermes geometry.
Figure 1d - Histogram of arrival times of first electron for the old prototype.
Figure 2d - Histogram of arrival times of first electron for the new prototype.
Figure 3d - Histogram of arrival times of first electron for the Hermes geometry.
5
Cathode:
2000
1800
1600
2000
1800
1600
Field
4
Cathode:
2000
1800
1600
2000
1800
1600
Field
3
Figure 1a - ep profile at front chamber for minitorus off, no radiation
Figure 2a - ep profile at back chamber for minitorus off, no radiation
Figure 1b - ep profile at front chamber for minitorus off, final version
Figure 2b - ep profile at back chamber for minitorus off, final version
Figure 1c - ep profile at front chamber for minitorus on, final version
Figure 2c - ep profile at back chamber for minitorus on, final version
Figure 1d - ep profile at front chamber for minitorus off, final version, 3 octants
Figure 2d - ep profile at back chamber for minitorus off, final version, 3 octants
2
We've had to change the location of the middle chambers to make room for the main magnet support structure. They are now between the two parts of the primary collimator. This means our ep peak is slightly smaller, but it is also closer to the beamline.
This plot shows the top three octant's ep peak at the two middle chamber locations. The minitorus was on with the highest current density.
1
This picture shows the mollers being bent by the minitorus. They are sometimes scattered off of the beam shielding and make it into the collimator acceptance.
