Changing the pion stop rate
The pion stop rate is changed by varying the slit width of FSH51, while
FSH52 define the momentum band and should stay untouched at 80. When
changing the stop rate, the prescaling factors also needs to be modified,
in order to give correct trigger rates for the computer. This is done
at the LB500 Prescaler unit by downloading a new schematic. Since different
schematics have different propagation delays, the timing at the LB500 MIX
units needs re-adjustmes, which is done by setting the LRS4518 MIX delay
unit.
The correct prescaling factors should lead to trigger rates of ~20-30 for
Pienu events, ~5-10 for PienuLo events, ~2-5 for prompt and random events
and <1 event for others.
Following table contains links to the various files for different stop
rates:
| Rate [/sec] | Set-Point file | Prescaler circuit
| Prescaling factors | LRS4518 MIX |
|---|
| 50k
| pb00_50k.set
| div_50k.jed
|
| PiStop | 64 |
| Pienu Hi | 1/8 (1) |
| PiBeta Lo | 16 |
| Pienu Lo | 516 |
| Three | 2 |
| HiLo | 1 |
| PiBeam | 128 (2) |
| eBeam | 1 (2) |
| Cosmic | 1 |
| del_50k.odb
|
| 200k
| pb00_200k.set
| div_200k.jed
|
| PiStop | 256 |
| Pienu Hi | 4/32 (1) |
| PiBeta Lo | 128 |
| Pienu Lo | 4096 |
| Three | 8 |
| HiLo | 1 |
| PiBeam | 512 (2) |
| eBeam | 4 (2) |
| Cosmic | 2 |
| del_200k.odb
|
| 800k
| pb00_800k.set
| div_800k.jed
|
| PiStop | 1024 |
| Pienu Hi | 16/128 (1) |
| PiBeta Lo | 1024 |
| Pienu Lo | 16384 |
| PiBeam | 2048 (2) |
| eBeam | 16 (2) |
| Cosmic | 2 |
| del_800k.odb
|
| 1300k
| pb00_1300k.set
| div_1300k.jed
|
| PiStop | 2048 |
| Pienu Hi | 32/256 (1) |
| PiBeta Lo | 2048 |
| Pienu Lo | 32768 |
| Three | 256 |
| HiLo | 16 |
| PiBeam | 4096 (2) |
| eBeam | 32 (2) |
| Cosmic | 2 |
| del_1300k.odb
|
| (1) changable via /Equipment/trigger/settings/Prescaling |
| (2) plus external prescaling |
To activate these files, do the following:
Set-Point file
Copy these files to pc1529 at c:\optima, if the are not already there. The press "Diskset" in the
set-point program and load the file.
Prescaler circuit
These files program the LB500 Pre unit at the trigger electronics. Copy the file to pc1529
under e:\isptools\pibeta\divider\divider.jed, overwriting the current file. The go down
at the trigger frontend and double click on the "Download Prescaler" icon.
LRS4518 Mix
Note: As from April 2000 on, the delays for ass stopping rates are
identical and need not to be loaded
These are the delay settings at the trigger mix input. Copy the files to pc2106 at the ~/online
directory and load the with odbedit like
$ odbedit
[local]/> load del_500k.odb
The frontend then takes care for forwarding the values to the CAMAC delay unit.
S. Ritt, August 2nd, 1999