Hi Rate Tests

[Elton Smith <elton@jlab.org>]

Hi Rate Test  (Elton Smith 11/23/99)
============

Here is a brief description of the results, followed by the program used
to take data.


Summary ======= In order to estimate background rates for Hall D, we
conducted a 1 hr test of high intensity running with photons at the end of
the g1 running period. We measured rates in the forward TOF (7.5-12.5 deg)
scintillators, the electromagnetic calorimeter (8-45 deg) and currents in
the drift chambers. All rates were linear in beam current. At the highest
electron current (320 nA), the rates in the detector were slightly higher
than the rates during data taking with an electron beam (4 GeV) with CLAS.
Considering that the electron data is analyzable, we conclude that the
hall D detector should be able to handle rates up to 10**8 photons/s.

Plots of the data can be found at 
http://claspc10.cebaf.gov/~elton/halld/trigger/review/



                |------------pmts----------------------|--drift
chambers--|

Photon Beam     TOF (forward)    EC    Start  Mor(note2)  r1    r2    r3
Current (nA)     (KHz) (note)   (KHz)   (MHz)    (MHz)       (micro A)

10                0.24           2.24    0.25     9.3     20.   27.   27.   
80                1.93           2.83    1.88     4.22   171.   75.  116.
250               6.00           8.13     -      11.2    477.  192.  309.
320               7.72          11.8      -      17.1    581.  231.  376.

4GeV Electron
4 nA current      6.87           9.57     -        -     444.  342.  299.
(typical)

     
General: To scale above currents (Hall B) to Hall D conditions, multiply
by the collimation factors 0.8/0.15 = 5.33. For example, 80 nA above
corresponds to approximately 430 nA in Hall D, where 300 nA corresponds to
nominal low current operation (10**7 photons/s).

note1: TOF and EC rates are averaged for sectors 1-4. Sectors 5 and 6 are
a factor of two higher than other sectors due to incomplete photon beam 
shielding.
note2: Mor (master Or rate) is the full tagger for 10 nA, T1-8 for all
other data.


Occupancies for each superlayer:
(logbook entry #7031), Run number 21998.


          At 320nA we find the following DC occupancies (%): 
              S1     S2     S3    S4    S5    S6
              2.3    2.3     0.3   0.4   0.7   0.9



-----------------------------------------------------------------------------


11/19/99 Hi Rate Test
On Shift: Volker Burkert, Dinko Pocanic, Vardan Gurjyan, Barry Ritchie,
Elton Smith


Program


Here is a proposal for the high intensity run tonight at 9:30.
Note: At 2.4 GeV, the 1 KW limit (80% Safety Factor) on the beam dump 
allows running up to 320 nA.

Conditions:
(Radiator = 10**-4 for entire run)

1. Target Full. 
2. L1 = nominal G1 TIGRIS trigger (OR of all TOF counters).
3. Configuration = G1_PROD_RR.
4. Turn HV off for T counters T9-61. T1-8 were the counters used by the G6
open trigger configuration. 
5. Turn HV off E49 (HVe1-12 on) and up (corresponding to T9-61).
6. E*T coincidence ON.
7. PC out of the beam.
8. PS converter out.
9. PS counters off.

Note: The prescale factor can be set using the old ts_config GUI.


1)

I=80 nA
T1-8
Trigger Mor*Start*L1 (G1 production)
Prescale = 9+1

Record:
1. Trigger Rate
2. Dead Time
3. Record Drift Chamber Currents
4. From Beam GUI
   Start Counter Rates
   Scintillator Rates
   EC Rates
5. Print out Scalers (end of run)

Take Data 10 min.



2)

I=250 nA
T1-8
Trigger Mor*L1. Start Counter OFF (Must use Expert Photon GUI)
Prescale = 500+1

Record:
1. Trigger Rate
2. Dead Time
3. Record Drift Chamber Currents
4. From Beam GUI
   Scintillator Rates
   EC Rates
5. Print out Scalers (end of run)

Take Data 10 min. Trigger rate ~ 2400 Hz, 12MB/s


I=320 nA
T1-8
Trigger Mor*L1. Start Counter Off
Prescale = 700+1

Record:
1. Trigger Rate
2. Dead Time
3. Record Drift Chamber Currents
4. From Beam GUI
   Scintillator Rates
   EC Rates
5. Print out Scalers (end of run)

Take Data 10 min. Trigger rate ~ 2400 Hz



Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625