So-called factor of ~2 problem • Just to share my experience of what I have found … Kin Yip C-AD Nov. 6, 2008
Long time ago, I made a picture of the attenuation settings in the AGS shaper board. • putting in a terminator turns off the LED (~kind of opposite); • it can also be set by software talking to the CAMAC chassis; • attenuations are very rough. http://www.c-ad.bnl.gov/kinyip/AGS-CNI/attenuations.gif
With an input signal of amplitude of ~0.34 V (square wave, NEG) directly to the shaper board--- which allows me to test all valid attenuations at once, I'd see : would give me ~220 (+/-20 or something) on ADC with the so-called attenuation 1/1; would give me ~110 (+/-10 or something) on ADC with the so-called attenuation 1/3;would give me ~55 (+/-10 or something) on ADC with the so-called attenuation 1/5;would give me ~25 (+/-10 or something) on ADC with the so-called attenuation 1/10; So, the attenuations of 1/3 is more like ~1/2.x, and 1/5 is more like ~1/4 and 1/10 is ~1/9, roughly speaking.
In the 2008 run, both terminators were plugged • attenuations ~1/10. • But traditionally (pre-2008 runs) --- which can be viewed from the yljet.ini : • OutReg=0x1000 // Set output register. Bits: - normal run • // ….. • It’s setting one of the 2 bits and that if you let the software set, you'll see that the LED's show ON/OFF --> the 1/5 --- which is also verified by pulse signal expts.
Injecting a pulse signal (NEGative square wave) of 0.344 V directly to the shaper boards with all the signal channels terminated in the usual setting and with ~1/3 attenuation, one would see the following:
If one sends a signal (NEGative square wave) of 0.588 V to the pre-amplifier in the RHIC tunnel with termination by a T (one side to terminator and the other side to pulse signal) with ~1/5 attenuation (at the shaper boards), you'd see:
With ~1/10 attenuation, the calibration () signals with the entire chain of real detector & electronics look like the following (with a peak near 110) : The calibration (~energy/ADC) in the calibration file very roughly ~50 etc.
With ~1/5 attenuation, the calibration () signals with the entire chain of real detector & electronics look like the following (with a peak near 220) : with fan off Just like in the past years, the calibration (~energy/ADC) in the calibration file ~22 or 25 etc.
Last words : • In HJET setup, the attenuations in calibration and normal data taking are the same. This “good” feature renders people not to remember what the attenuations should be. • The factor of 2 is due to the attenuation differences. • It’s different for the CNI and somehow I have had to remind myself at least once a year what the attenuations for calibration and normal data taking in AGS are.