CDC recent run drift times

Fitted drift time function to straws in run 2451, picked straws with tmax slope < 30, used same straws for subsequent runs. Used same hit thresholds & window for all runs.

The drift times are for a small group of straws. In the earlier runs the amplitude histograms are cut off at the lower end by the sparsification threshold. There are a few straws with noise (and threshold) low enough that the MPV is visible. The max amplitude histograms show entries below the sparsification threshold because I used a lower threshold for analysis, added to the pedestal just before the peak; often there is a smaller peak before a larger one; less often the pedestal rises between the start of the data window and the peak.

1 Summary up to run 2713
2 Run 2451 - solenoid off
3 Run 2551 - solenoid off
4 Run 2560 - solenoid off
5 Run 2577 - solenoid off
6 Run 2616 - solenoid at 1200A
7 Run 2617 - solenoid at 1200A
8 Run 2619 - solenoid at 1200A
9 Runs 2616 to 2619 combined - solenoid at 1200A
10 Run 2642 - solenoid off
11 Run 2644 - solenoid off
12 Run 2649 - solenoid off
13 Run 2676 - solenoid off
14 Run 2688
15 Run 2692 - solenoid off
16 Run 2713 - solenoid off
17 Run 2839 - solenoid off

Summary up to run 2713

Removing alcohol decreased max drift time by 20ns and decreases gain by at least 20%.
Decreasing CO2 gas conversion factor from 0.773 to 0.74 increased max drift time by 8s and decreased gain slightly (difficult to quantify the gain decrease).
Moving the CO2 from controller CH2 to 4 and switching the mixer from rate to blend and back caused only very small changes, if any.
Changing the CO2 gas conversion factor from 0.74 to 1.0 decreased max drift time by 70ns and increased gain x 236%

Run 2451 - solenoid off

7 Feb 2015. First run of 2015. Increased sparsification thresholds from 7sigma to 15sigma.
Garfield 0T 55.78% Ar 43.82% CO2 0.4% 2-propanol (0.4% propanol added to mix of 56% Ar + 44% CO2) has t 561ns @ 0.76cm, tmax 577ns @ 0.77cm
Adding 0.5% 2-propanol to 56/44 Ar/CO2 gives Garfield t of 565ns @ 0.76cm and 1% 2-propanol gives Garfield t of 590ns @ 0.76cm
With a gas mix of 65/44, time < (550-t0) x 0.8ns = 66ns corresponds approximately to drift radius < 2.9mm

Hit thresholds 180-100-25, window 44-150
Drift time fit straws with param 6 < 30	drift time fit zoomed in	pedestal	max amplitude vs time	max amplitude - pedestal, time < 550, straw 1021	max amplitude - pedestal (all)

Run 2551 - solenoid off

2-3 March 2015. 3 weeks after disengaging the alcohol bubbler.
Compared with run 2451, drift velocity has increased and gain decreased (but cannot measure the gain decrease very well due to thresholds).
Garfield 0T 56% Ar 44% CO2 has t ~543ns @ 0.76cm, 558ns @ 0.77cm
Garfield 0T 57% Ar 43% CO2 has tmax ~543ns @ 0.77cm

Hit thresholds 180-100-25, window 44-150
Drift time fit straws with param 6 < 30	zoomed in	pedestal	max amplitude vs time	max amplitude - pedestal, time < 550, straw 1021	max amplitude - pedestal (all) \|}

Run 2560 - solenoid off

8 March 2015. 5 days after changing the CO2 gas factor from 0.773 to 0.74 (should result in increase in CO2 %). The gas factor was changed before run 2552.
Comparing with run 2551, drift velocity and gain have both decreased slightly (consistent with more CO2).

Hit thresholds 180-100-25, window 44-150
Drift time fit straws with param 6 < 30	zoomed in	pedestal	max amplitude vs time	max amplitude - pedestal, time < 550, straw 1021	max amplitude - pedestal (all)

Run 2577 - solenoid off

10 March 2015. 1 day after changing the gas mixer MFCs from master/slave "blend" to independent "rate" mode (this change was made before run 2563). For this run the readout window is different from that in all the others.

Hit thresholds 180-100-25, window 64-170
Drift time fit straws with param 6 < 30	zoomed in	pedestal	max amplitude vs time	max amplitude - pedestal (all)

Run 2616 - solenoid at 1200A

11 March 2015. 2 days after changing the gas mixer MFCs from master/slave "blend" to independent "rate" mode.
Drift times increased substantially due to the magnetic field. Amplitude not inconsistent with that from run 2560 (lower stats in this run).
Garfield 1.75T 56% Ar 44% CO2 has t ~597ns @ 0.76cm, 613ns @ 0.77cm
Garfield 1.75T 57% Ar 43% CO2 has tmax 603ns @ 0.77cm
Garfield 1.75T 57.5% Ar 42.5% CO2 has tmax 596ns @ 0.77cm

Hit thresholds 180-100-25, window 44-150
Drift time fit straws with param 6 < 30	zoomed in	pedestal	max amplitude vs time	max amplitude - pedestal, time < 500, straw 1021	max amplitude - pedestal (all)