SCALERS  PRIOR  TO  OCT 2003

R. Michaels,  Jefferson Lab,  e-mail:  rom@jlab.org,  updated Oct 29, 2003

The scalers have been pretty stable in physical layout for years. In the long shutdown of Fall 2003 I decided to add a bunch of scalers and to rearrange the helicity gated scalers so that the only redundancy was between two spectrometers; this liberated some channels. Here is the record of the arrangements prior to these changes.

Scalers count raw hits on phototubes, as well as  important quantities like charge and triggers which are used to normalize the experiment.  The scalers are read online using the "xscaler" code, and the meaning of the channels is evident from the scaler configuration file which that code uses.  The scaler config file is normally located in the directory from which you must run "xscaler", namely ~adaq/$EXPERIMENT/right/scaler ~adaq/$EXPERIMENT/left/scaler where $EXPERIMENT is an environment variable like e94104.   I typically save these config files in the Mass Storage System, see the stubfiles /mss/halla/$EXPERIMENT/raw/*scaler*

We attempt to keep the channel mapping the same to avoid driving anyone crazy, but some changes are inevitable.   For the time after Fall 2003, e.g. hypernuclear experiment e94107, see dstruct.html.   For years prior to 2002, see dstruct_year2001.html   and   dstruct_pre2001.html

The number of scaler channels in a bank is determined by the lowest 6 bits of the header. Some scaler have 16, others 32 channels. The helicity gated scalers are FIFO scalers run in G0 helicity mode, see also www.jlab.org/~rom/g0helicity.html.   Since there are two redundant scalers, there are two redundant copies of the helicity gated data.

Arrangement of  the Right   Spectrometer   Updated Jan, 2003

Bank of 16 or 32 Channels	Header	Usage
1st  Bank	0xceb00020	1-6=S1-Left, 7,8=blank, 9-13 and 15 =S2-Left, 14,16=blank, 17-22=S1-Right, 23,24=blank, 25-29 and 31 =S2-Right, 30,32=blank.
2nd  Bank	0xceb20010	Left.AND.Right PMTs: 1-6=S1, 7,8=blank, 9-13 and 15 =S2, 14,16=blank.
3rd  Bank	0xceb30010	1-10=Gas Cerenkov PMTs, 11=GasC-sum
4th  Bank	0xceb50010	EDTM Scaler
5th  Bank	0xceb60010	Spare channels
6th  Bank	0xceb70020	Plus Helicity gated normalization data. Channels 1-32 follow the same map as channels 1-32 of the ceb8 scaler.
7th  Bank	0xceb80020	Normalization Data not gated by helicity   channel 1=T1, 2=T2, 3 Upstream(x10)BCM, 4=MLU-Strobe, 5=Hel+ pulses, 6=Hel- pulses, 7=Upstream(x3)BCM, 8=1024Hz-clock, 9=Unser, 10=Downstream(x3)BCM, 11=Downstream(x10)BCM, 12=blank, 13=TS-accept(IF R-arm TS), 14=Upstream(x1)BCM, 15=EDT-Pulser, 16=Downstream(x1)BCM. 18 = helicity transitions, 19 = QRT, 20 = MPS, 21 = LNE, 22=T3 from L-arm, 23=T4 from L-arm.
8th  Bank	0xceb90020	Minus Helicity gated normalization data. Channels 1-32 follow the same map as channels 1-32 of the ceb8 scaler.
9th  Bank	0xceba0010	1st channel = 100 kHz clock. Other channels unused at present.
10th  Bank	0xcebb0020	This is the 2nd FIFO scaler for helicity plus gated data.
11th  Bank	0xcebc0020	This is the 2nd FIFO scaler for helicity minus gated data.

The scalers are cleared at the beginning of a run, and read out finally at the end of the run. The timing of the gates, which enables the scalers to count, is such that the end-of-run scaler readout is done after gates are turned off, and then after this final readout the gates are re-enabled, so that scalers can count in between runs. The end-of-run scaler data are written automatically to a file on ~a-onl/scaler/scaler_history.dat. Routines exist for reading this file and pulling out the particular scaler channel.

Scaler data are also inserted into the data stream as an event type 140 typically every 4 seconds, but not synchronized to any other event. The capability to read scalers at 30 Hz with zero deadtime is also supported, and these data appear as ROC10 and ROC11, see section below. New in May 2003, an event type 100 is written at end of run which has same format as ROC10/11 which is the final scaler reading from ROC10/11. Also new are the "TS2 scalers" which are scalers on the new trigger supervisor, see ROC10/11 section below.

•   Trigger Supervisor Crates (ROC10 or ROC11, and TS2 Scalers)

TS2 SCALERS :     The new trigger supervisor TS2 has scalers on board. This "TS2 scaler" data was available after March 31, 2003. The data starts with header 0xfed00015 in the ROC10 ring buffer readout (see scaler_roc10.html link above). Firstly, the 0x15 in lower bits encodes how many data follows. These data are the 21 scaler data from TS2 registers. Here is the format:

scaler 1 = trigger 1 input, i.e. after prescaling
2 = trigger 2
3 = trigger 3
same 4,5,6... 12
13 = "OR" of triggers
14 = Level 1 accept (can use this as alternative to external scaler L1A)
15 = scheduled sync's
16 = programmed events (normally zero unless I program special events)
17 = latched triggers
18 = program 2 events
After these 18 scalers are 3 more data that come from TS2 registers:
19th = Event count
20th = Live 1 count (see below)
21st = Live 2 count
---------------
Live 1 count = free running 200 kHz clock gated by DAQ live signal (.NOT. busy)
Live 2 count = same clock, no gate.
Live Time = (Live 1 count) / (Live 2 count) <= 1.0
(However, this live1/live2 ratio only works if psfactor=1.  
If psfactor!=1 it is wrong because it incorrectly assumes random trigger.)

The TS2 scalers are latched at start of ring buffer readout 
to avoid time slewing.  The latch is freed after a read, but 
the latching doesn't affect the actual counting.