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Subsections

The Scaler GUI

Overview

The scaler GUI puts on one screen the result of the 16 entries of the Joerger Scaler located in the classc3 crate in Hall B. It's mainly connected to 11 detectors around the beam to measure the beam halo, see Chapter 5.

How to launch it

Launching the GUI is very easy once the GUI_launch GUI (see section 4.2) is up. Simply click on the left popup menu and select 'scaler'. A window (Figure 4.4) should shortly pop-up on the screen.

**Figure 4.4:** The Scaler GUI window
$\begin{figure} \epsfysize=15cm \centerline{\rotatebox{-90}{ \epsfbox {scaler_gui.eps} }}\end{figure}$

How to use it

What to look at ?

The important information is at the top of the GUI. On the left, the Faraday cup current is displayed, when the value is too low the background becomes black, and a string appear saying 'no beam'. Of course, this is pertinent only if we are running in electrons, the Faraday cup only responds to electron beam current.

On the right is the sum of the 4 upstream beam-halo counters. If the beam is badly aligned, the counting will increase dramatically. The background will turn orange and then red, and a warning string will be displayed.

What to do ?

The scaler has an auto-start mode and you don't need to touch anything to make it work properly. If the thresholds for bad beam are not set correctly, they can be modified using the red pop-up menu in the lower right part of the window. Select 'Threshold adjustment', then it's straightforward.

The red alert will remain on the screen even after the beam has been tuned better. To reset the warning string, click on the 'reset' button at the middle of the top part of the display.

Table 4.8: The Scaler Summary Panel
[1] 2l|The Summary Panel

[1.a] The beam current measured by the Faraday Cup in nA. Only meaningful in electron run.

[1.b] The sum of the 4 upstream counters. A good one eye look into the beam presence and quality (too low : no beam, too high : bad beam).

[1.c] The Beam Warning-String Area. Can display one of the following:

Nothing
Everything seems OK for it.
No Beam
The Faraday Cup current is too low. No Electron beam.
Beam's getting bad !
The Sum [1.b] has reached the orange threshold alert level.
Bad Beam !
The Sum [1.b] has reached the red threshold alert level.

[1.d] The string ``Red Alert Occurred !'' will be displayed once the critical real level has been reached, and will persist even after a better tuning has been made. It will be erased by clicking on the [1.e] ``reset'' button.

[1.e] Erase the ``Red Alert Occurred !'' (see above).

**Table 4.8:** The Scaler Summary Panel
[1]	2l\|The Summary Panel
	[1.a]	The beam current measured by the Faraday Cup in nA. Only meaningful in electron run.
	[1.b]	The sum of the 4 upstream counters. A good one eye look into the beam presence and quality (too low : no beam, too high : bad beam).
	[1.c]	The Beam Warning-String Area. Can display one of the following: Nothing Everything seems OK for it. No Beam The Faraday Cup current is too low. No Electron beam. Beam's getting bad ! The Sum [1.b] has reached the orange threshold alert level. Bad Beam ! The Sum [1.b] has reached the red threshold alert level.
	[1.d]	The string ``Red Alert Occurred !'' will be displayed once the critical real level has been reached, and will persist even after a better tuning has been made. It will be erased by clicking on the [1.e] ``reset'' button.
	[1.e]	Erase the ``Red Alert Occurred !'' (see above).

Table 4.9: The Scaler Upstream PMTs Panel
[2] 2l|The Upstream PMTs Panel

[2.*] The counts are displayed according to the Control Panel [7]. The actual counters are disposed as follow : (a : up) (b : down) (c : south) ( d : north). The e indicator displays North South coincidences.

**Table 4.9:** The Scaler Upstream PMTs Panel
[2]	2l\|The Upstream PMTs Panel
	[2.*]	The counts are displayed according to the Control Panel [7]. The actual counters are disposed as follow : (a : up) (b : down) (c : south) ( d : north). The e indicator displays North South coincidences.

Table 4.10: The Scaler Downstream PMTs Panel
[3] 2l|The Downstream PMTs Panel

[3.*] Every remark made on the panel [2] apply to the Downstream PMTs Panel (except that there are no coincidences).

**Table 4.10:** The Scaler Downstream PMTs Panel
[3]	2l\|The Downstream PMTs Panel
	[3.*]	Every remark made on the panel [2] apply to the Downstream PMTs Panel (except that there are no coincidences).

Table 4.11: The Scaler Tagger PMTs Panel
[4] 2l|The Tagger PMTs Panel

[4.*] Every remark made on the panel [2] apply to the Tagger PMTs Panel (except that there are no Down PMTs).

**Table 4.11:** The Scaler Tagger PMTs Panel
[4]	2l\|The Tagger PMTs Panel
	[4.*]	Every remark made on the panel [2] apply to the Tagger PMTs Panel (except that there are no Down PMTs).

Table 4.12: The Scaler Raw Data Panel
[5] 2l|The Raw Data Panel

[5.*] Everyone of the 16 channels of the Scaler are displayed here. The raw 32 bits values are not affected by the display mode [7.c].

**Table 4.12:** The Scaler Raw Data Panel
[5]	2l\|The Raw Data Panel
	[5.*]	Everyone of the 16 channels of the Scaler are displayed here. The raw 32 bits values are not affected by the display mode [7.c].

Table 4.13: The Scaler Latched Raw Data Panel
[6] 2l|The Latched Raw Data Panel

[6.*] Everyone of the 16 channels of the Scaler are displayed here. The raw 32 bits values are not affected by the display mode [7.c]. But the value displayed is the one previously reached at the end of the last count, and is updated each time the scaler ends a count run.

**Table 4.13:** The Scaler Latched Raw Data Panel
[6]	2l\|The Latched Raw Data Panel
	[6.*]	Everyone of the 16 channels of the Scaler are displayed here. The raw 32 bits values are not affected by the display mode [7.c]. But the value displayed is the one previously reached at the end of the last count, and is updated each time the scaler ends a count run.

Table 4.14: The Scaler Control Panel
[7] 2l|The Control Panel

[7.a] The action of this button depends of the state of the [7.b] button. In Continuous Mode, clicking ``count'' will start the scaler, and it will indefinitely stay in acquisition mode. Clicking ``Done'' will just cancel the Current acquisition, but the next one will began immediately. In ``One Shot'' Mode, clicking ``count'' will make the Scaler perform one acquisition, and then stop. Clicking ``Stop'' will stop the current acquisition and the scaler will remain idle ¹¹.

[7.b] Continuous run or one run and stop. See above for details.

[7.c] The values in the panels 2 3 and 4 will be affected by this toggle button.

Raw
The raw count is displayed
Hertz
The value is normalized in Hertz
Norm
The value is normalized by the Faraday Cup current (the displayed result is in counts/s/nA).

[7.d] The acquisition time. Time during which the scaler will accumulate counts before stopping the acquisition (and resetting and restarting if in continuous mode).

**Table 4.14:** The Scaler Control Panel
[7]	2l\|The Control Panel
	[7.a]	The action of this button depends of the state of the [7.b] button. In Continuous Mode, clicking ``count'' will start the scaler, and it will indefinitely stay in acquisition mode. Clicking ``Done'' will just cancel the Current acquisition, but the next one will began immediately. In ``One Shot'' Mode, clicking ``count'' will make the Scaler perform one acquisition, and then stop. Clicking ``Stop'' will stop the current acquisition and the scaler will remain idle ¹¹.
	[7.b]	Continuous run or one run and stop. See above for details.
	[7.c]	The values in the panels 2 3 and 4 will be affected by this toggle button. Raw The raw count is displayed Hertz The value is normalized in Hertz Norm The value is normalized by the Faraday Cup current (the displayed result is in counts/s/nA).
	[7.d]	The acquisition time. Time during which the scaler will accumulate counts before stopping the acquisition (and resetting and restarting if in continuous mode).

hardware and software

The scaler GUI uses the Joerger Scaler, ands thus, the records and hardware detailed in Section 3.2.4. It runs in the classc3 IOC. The PMTs are located as shown in Figure 2.11 and 2.12.

The acquisition system is very basic. As seen in Figure 4.5, the incident particle crosses the scintillator, inside which it creates light. Then the light falls onto a PMT that converts it to electrons and amplifies it. This analog signal is then sent to a discriminator that will output a logic ``1'' pulse for each analog pulse above a certain threshold. The output pulses of the discriminators are counted by the scaler.

**Figure 4.5:** Halo acquisition principle
$\begin{figure} \epsfysize=12cm \centerline{\rotatebox{-90}{ \epsfbox {scaler_acq.eps} }}\end{figure}$

The software for the scans is detailed in chapter 5. The computation of the normalized scaler data are made using a lot of computation records (Section 3.2.2), an SNL routine provide automatic restart of the scaler when idle for more that 30 seconds. An experimental ``fast scan'' has been implemented, see section 4.8.

File informations

The application is under CVS monitoring and is known as scaler. To check it out, type cvs checkout scaler. It can by built using the make command in the main directory.

There are several files of interest :

scaler/db/scaler.db: is the database file. Outside the scaler record itself, there is heavy use of different computation records to process the raw data before displaying them.
scaler/medm/scaler.adl: is the main GUI, written with medm.
scaler/medm/fcup.adl: is the small GUI displaying only the Faraday Cup current.
scaler/src/scaler_restart.st: contains the subroutine that automatically restarts the scaler.
scaler/src/scaler_warning.st: contains the subroutine that displays the different quality levels of beam when needed.
File part of the ``fast scan'' routines: scaler/medm/scaler_dsp.adl : the GUI,
scaler/src/data_analyse.c, scaler/src/data_analyse.h, scaler/src/fft_resources.c, scaler/src/sampling_routines.c, scaler/src/sampling_routines.h, scaler/src/scaler_acquisition.st. See Section 4.8.

Footnotes

...idle¹¹: The scaler has an autostart feature that restart it after 30 second of idle time.

Next: The Collimator GUI Up: Beamline EPICS applications Previous: The Harp GUI

Garp patois@cebaf.gov