Log entry time 10:41:05 on March17,2009

Entry number 266516

This entry is a followup to: 265609

This is a test with 1 kHz MPS sequence.
Actually the rate is R = 1/(W+S)
where W = integrate window = 980 usec
S = settling time = 10 usec (can be up to 500 usec)
So, R = 1.01 kHz here

Reminder: I did deadtime measurements at 30 Hz with 
prescales up to 25, see halog 265609.

We vary our own ramp delay and oversampling using
the HAPPEX timing board.  Here, ovs=1 means no oversampling,
and ovs=4 means 4 oversamples (in the code these are 0,3 resp.)
The units of ramp delay and integ window are 2.5 usec

Run .... Ovs .... Ramp .... Integ 

31059 ... 1 ...... 20 ..... 100
31060 ... 1 ...... 20 ..... 300
31061 ... 2 ...... 0 ...... 125
31062 ... 2 ...... 0 ...... 129
31063 ... 4 ...... 0 ...... 30
31064 ... 4 ...... 0 ...... 10
31065 ... 4 ...... 0 ...... 30
31066 ... 8 ...... 0 ...... 7 ... complete breakdown (high DT)
31067 ... 4 ...... 0 ...... 10
31068 ... 1 ...... 0 ...... 10
31069 ... 1 ...... 0 ...... 310
31070 ... 1 ...... 0 ...... 400 ... deliberately 50% DT 
31071 ... 1 ...... 20 ..... 300
31072 ... 2 ...... 20 ..... 120
31073 ... 3 ...... 0 ...... 75

Indications of deadtime are:

1. Scope measurements of the busy from TIR, and of the TS input.
2. CODA GUI rate
3. Run pan, observe pair sequence errors and event sequence errors.
4. Look at scaler for TS input and TS accept
scaler0_30 = TS input (should peak at 1)
scaler0_31 = TS accept (should peakt at 1)

The first hint of a small DT occurs at 3 kHz.
At 4 kHz the DAQ starts to break down and it falls apart at 8 kHz.

The region around 4 kHz could be explored further, as
there could be some misunderstanding of the timing setup :
strangely, runs 31064/67 had more deadtime than 30163/65.
In 31064/67 the DT was clearly 50% on a scope and the
observed rate was 2 kHz in CODA, the data came in bursts
of 3 followed by 3 blanks.  (This is at 4 kHz).

Tentative conclusion: It seems we can run up to 2 kHz, or
200 Hz with ovs=10, or 240 Hz with ovs=8.  Maybe higher,
but needs to be investigated.

Note, Alex ran the Compton DAQ which, as expected, totally
broke down at 1 kHz.   

What we need is a sliding trombone of flip rate, like 30, 
60, 120, 240 ...