# Presentation: 261079

## ICD LED Run Status

**Purpose**
**ADC to GeV Conversion**
**Basics of ICD LED Pulser**
**Taking Runs**
**Looking at the data**
**What’s next?**

## Purpose of LED Runs

**Long term monitoring of PMT response**
**The photomultiplier tubes for the Run II ICD sub-detector were *****recycled***** from the Run I ICD boxes**
**Each channel was individually *****tuned***** in order to achieve a mean MIP peak on the cosmic ray test stand**
**Only lever arm is the high voltage setting**
**Over a dozen PMTs have already been replaced**
**About a dozen channels have failed or dropped significantly in gain since the end of the Oct-Nov shutdown**
**Establish a real world baseline for the full ICD – from scintillator tile to the BLS card**
**Determine correction for channel to channel variation**

## ADC to GeV Conversion 

**Specific energy loss (dE/dx) in the Bicron BC-400 scintillator (PVT)**
**      ****dE/dx****min****= 1.956(g/cm****2****) ******** 1.032 g/cm****3**** = 2.02 MeV/cm**
**Mean MIP peak in test stand ADC counts for 368 channels was 135.7 ****(aim was 140!)**
**Relative gain factor between calorimeter preamps (used on the test stand) and the ICD preamps was 3.8.**
**Extra amplication of 8.7 used to boost signal on test stand**
**Factor of 10 between least count of test stand ADCs and the calorimeter ADCs.  Least count for test stand ADC is 1 mV and calorimeter ADC is 0.1 mV.**

*Interlude borrowed from *
*talk given by Andy White*
*16 Jan 2002 at Jet Energy Scale Mtg*

## ADC to GeV Conversion 

**The *****cosine***** factor accounts for angle from normal to an ICD tile relative to a straight line drawn from the IP through the center of a tile.  There are three numbers, one for each ieta bin spanned by the ICD:**
**            **_**ieta**_**                  **_**cosine factor**_
**	****	****   ****12****	****	****    0.592**
**	****	****   ****13****	****	****    0.633**
**                 ****14****	****	****    0.671****	**
***NOTE: sampling fractions also include this angular factor, so one must be careful not to apply it twice!***
**Thickness of all ICD tiles are 0.5 in (about 1.27 cm).**

***Interlude continued***

## ADC to GeV Conversion 

**Average MIP peak position in calorimeter ADC counts is given by:**
**    ****(135.7 ******** 10) / (3.8 ******** 8.7) = 41.0 counts**
**The energy deposition in an ICD tile is given by:**
**    ****(Cal. ADC count / 41.0) ******** (2.02 MeV/cm ******** 1.27 cm)**
**The result is:**
**     ****(Cal. ADC count ******** 0.06257) [MeV]**

***Interlude continued***

**=  (Cal. ADC count / 15982) [GeV]**

## ICD tiles – test stand resultscompiled by Mark Sosebee

## The Basics of the ICD LED Pulser

**Scintillator LED Pulser (SLP) – *****borrowed***** from the Muon calibration system**
**ICD shares VME board with FPD – sits in MCH308**
**Accepts external NIM test pulse trigger**
**VME controlled channel enable, trigger, amplitude and delay**
**Steve Doulas provided the documentation and expertise!**
**Excellent GUI created by Marc Hohlfeld!**
**DC offset resistively coupled to a TTL signal pulse**
**TTL pulse triggers a transistor which discharges a capacitor into a group of four LEDs**
**DC offset provides the bias voltage for these LEDs**

## Taking ICD LED Runs

**Detailed instructions now part of the Cal Shifters’ Guide  ****(thanks to Florencia for getting cal_elec to work!)**
**Needs to be given priority during periods without beam**
**A baseline still needs to be determined**
**What is the optimum delay time (between 0 and 170 ns)?**
**What DC offset(s) should be used?  **
**The turn-on voltage as seen on the oscilloscope directly**
**	****from the electronics is about 6.6 Volts.**
**The LED pulser needs to be issued a command to turn off during the prepare-for-run-1.1 download**
**There is currently no alarm to check that the ICD LED pulser is off during global data-taking**

## > setup d0online> cd /home/d0icd/vme> ./lmb_int.py &

**> setup d0online****> cd /home/d0icd/vme****> ./lmb_int.py &**

**More on  LED Pulser Runs**

**Voltage is adjustable up to 10.0 Volts in increments of 0.2 Volts**
**Delay is adjustable from 0 to 170 ns in increments of 2 ns**
**All Download is preferable – Read *****feature***** sets ALL to zero**

## What has been done?

**Several LED Runs taken by Pierre Petroff on Jan 23****rd**
**First test of instructions revealed that cal_elec was not working well enough**
**Stephanie Beauceron took the full set of runs (six DC offsets at six different time delays) on Feb 6****th****!**
**Too much work – need to reduce the number of steps  **
**hbook saved files very useful to make plots/printouts offline**
** ****Lee Sawyer created SAM datasets **
**still need more effort offline**

- Ted Elzroth determined ADC
- count value for one good channel
- from each Cal Crate in which
- the ICD is part of the readout -
- [Crates 0,1,4,5,6,7,10,11].  Did
- this for each DC offset & time
- delay setting – 8  6  6 = 288!

## All ICD channels in Cal Crates 10 & 11 readout

**All ICD channels in Cal Crates 10 & 11 readout**

## ICD in Cal Crate 0

## ICD in Cal Crate 1

## ICD in Cal Crate 4

## ICD in Cal Crate 5

## ICD in Cal Crate 6

## ICD in Cal Crate 7

## ICD in Cal Crate 10

## ICD in Cal Crate 11

## Next Step

**Take another series of runs**
**Step through delay times of 120-170 ns**
**Fewer DC offsets: 7.8, 8.2, 8.6 and 9.0 V**
**Fewer events per run to speed up the process**
**Do the plots and printouts offline**
**Why is there a significant timing difference between the ICD channels in different Cal crates?**
**Possible error?  Current method requires strict bookkeeping from the renaming of hbook files to filling the spreadsheet**
**SLP cable length difference between East & West**
**Purchase & test new PMTs **