# Presentation: 265840

**Impact of Run I/II Changes on Calibration**

**Leslie Groer**

- September 25, 2000

- DØ Offline Calibration Workshop
- Paris, France    September 25-29, 2000

## Outline

**Run I vs Run II Timings**
**BLS Operation**
**Signal Timing and Shaping**
**Faster Shaping**
**implications**
**Timing**
**effects of super bunches**
**Calibration**
**effects of faster timing**
**Noise**
**sources**
**Other Stuff**
**full scale**
**temperature dependence**
**linearity**
**trigger pickoff**

## Run II Parameters

## Run I vs Run II Timing

**3.56us**

**4.36us**

**2.64us**

**superbunch**

**gap**

**396ns**

**gap used to form trigger**
**and sample baselines**

**this gap is too small to**
**form trigger and sample**
**baseline**

**Bunch structure**

- Run I    6x6

- Run II 36x36

**Design all the electronics, triggers and DAQ to handle bunch structure with a minimum of 132ns between bunches and higher luminosity**
**We expect 3 gaps between superbunches – must be a multiple of 132 ns (7 RF buckets)**

## Run I vs Run II sampling

**Bunch crossing spacing was 3.5 ********s in Run I but will be 132ns in Run II (first level trigger decision ~ 4.2 ********s**
**Sample earlier ( ~320 ns instead of 2.2 ********s) dictated somewhat by LAr drift time (~450ns)**
**Pipeline events waiting for trigger decision**

**Run I**
**Signal = peak – base**
**-ve pileup, +ve multiple interaction**
**Run II**
**Signal = peak****N**** – peak****N-1**
**Zero average, +ve and –ve fluctuations**

## Run II BLS Operation

- input from preamp

- shaping

- analog storage (L1)

- baseline subtraction

- analog storage (L2)

- readout

- “Simple” RC circuit  shaper

## Signal Timing + Shaping

**Peak at about 300ns**
**return to zero by about 1.2********s**
**Sample at 320ns**
**Mostly insensitive to 396 ns or 132 ns running**
**BLS-Finite time difference is measured**
**Normal running uses three samples earlier**
**Pulser requires four samples earlier**

**Preamp output is integral of detector signal**
**rise time > 430ns**
**recovery time 15********s**
**Shaped signal sampled every seven RF buckets (132ns)**

**After shaper**

**Signal from preamp**

**0**

**400**

**1200**

**800**

**ns**

**amplitude**

**320 ns**

**Detector signal**

**Notes:**
Because the signal is faster, we need to adjust the sampling relative to the beam to a much higher precision.
Because the peak value will also be used as the baseline for a different bunch, signals uncorrelated to the accelerator clock average exactly to zero.
Energy which is uncorrelated to the trigger, but in synch with the beam will approximately average to zero.  Except for the first few in each superbunch.

As the recovery time of the shaped signal is about 1.2s, the bunches in the beginning of each superbunch will be slightly different from later bunches.
This effect is essentially independent of 396ns or 132ns running because the shaping time chosen.
Following the L1 decision, the reading with appropriate gain factor and relevant baseline 
subtracted is passed to L2 SCA (also analog)

Full scale Energy (not E_t) per cell
approx 100 GeV
except of EM 3-4 where it is approx 200 GeV
same as run 1....but
Linearity
First look is hopeful, but may still require more than the three numbers/channel used in run 1

## Effects of Faster shaping

**Want to decrease pileup effects **
** ****shaping time dictated by drift velocity in LAr **
** ****only use about 2/3 of the charge left in the detector**
**Pulser signal is injected at the preamp instead of inside the detector**
** ****the pulser response must be corrected for the difference**
**Cable lengths/capacitance important**
**Signal is faster**
** ****need to adjust the sampling relative to the beam to a much higher precision.  **
** ****This will require special data runs, and software to analyze the data.**

## Run I vs Run II Differences

**Because the peak value will also be used as the baseline for a different bunch, signals uncorrelated to the accelerator clock average exactly to zero**
**Energy which is uncorrelated to the trigger, but in synch with the beam will approximately average to zero (except for the first few in each superbunch)**

## Superbunch Timing

**Superbunch Timing**

**Beginning of “superbunch”**

**At 396 ns**

**bunch 1**

**bunch 2**

**bunch 3**

- No min-bias

- min-bias from bunch 1

- min-bias from bunch 2 + 25% of 1

**At 132 ns**

**bunch 1       2      3     4       5     6     7      8      9**

- No min-bias

- 5% of bunch 1

-       

-       

## Side effect of superbunch gaps

**Because of the recovery time of the shaped signal is about 1.2********s, the bunches in the beginning of each superbunch will be slightly different from later bunches.**
**Both the mean and the sigma due to pileup effects change during the first 1.2********s of each superbunch.  The mean starts at its maximum value while the sigma starts at it minimum.**
**This effect is essentially independent of 396ns or 132ns running because of the shaping time chosen.**

## Calibration

**Maximum response time for EM and hadronic channels differ. Model dependent corrections to the pulser response will have to be applied to correct for differences in when charge arrives at the preamp.**
**Will need to correct calibration pulser timing for different preamp types**
**Correct pulser response for different timings and shape compared to beam data**

- low capacitance cell

- high capacitance cell

- Signal reflection

**No test beam running ******** absolute energy scale will have to be established from the data**
**Use initial “guess” based on Monte-Carlo sampling weights and Spice models of the electronics.**

## Noise Sources

**Electronics**
**random**
**coherent**
**Uranium**
**High Voltage related**
**Pile-up**
**Luminosity dependant**
**position in the super-bunch**

- Coherent noise measurement
- from August 2000

- Pair-wise correlations
- between
- channels for 10k events

## Noise 

**Run I**
**Uranium noise dominated electronic**
**        ****e.g.**
**Run II**
**Electronic up by ********t and U noise down by same factor (********5.5=2.3**** ****). **
**2 FET input gives ********2 improvement**
**Pile-up noise: ******** x 1.3**
****** ****luminosity (~ ******** L)**
****** ****shorter shaping times (~ ******** t)**

| MeV | Elec. | U | Elec. + U. |
| --- | --- | --- | --- |
| EM | 4 | 7 | 8 |
| FH | 36 | 62 | 72 |

| MeV | Elec. | U | Elec. + U. |
| --- | --- | --- | --- |
| EM | 6 | 3 | 7 |
| FH | 58 | 27 | 64 |

- no pile-up

**Notes:**
 U noise dominant over electronic noise in RunI : Estimate rms U noise from RunI Zero Bias data      done by John Krane Then scale it to RunII by 1/sqrt(5.5) ..(Dean) (ICD/MGAP/CH set to 0)
 Electronic noise  Dean’s model in ADC counts : RMS (ADC)= sqrt(0.5**2+(0.9*Cd)**2) (Cd in nF from Dan Owen’s database)
 ADC --> Gev ? 
U_noise = Ele_noise in EM3 (Dean level 0)other layers RMS scaled from EM3 accordingto their capacitance

## Other Stuff

**Full scale Energy (not E****T****) per cell**
**approx 100 GeV**
**except of EM 3-4 where it is approx 200 GeV**
**same as Run I....but**
**Preamp temperature dependence**
**Unknown due to lack of manpower**
**Linearity**
**First look is hopeful, but may still require more than the four numbers/channel used in Run I **
**1 offset & 1 gain for each x1/x8 path**
**Trigger pickoff resistors**
**Initial guess based on Spice model**
**All 10k will need to be replaced...**

## Unknowns for  Online Calibration

**96 independent channels x DAC settings x delays**
**Use 32 patterns from Run 1 to start – is this the right granularity**
**Number of events needed per pattern or DAC setting**
**Need different timings for different cap’s**
**How long is length of quiet time for zero bias data/pulsed**
**Hope that calibration for ICD does not need to be separate but timing is not optimized for ICD signal. Would double the calibration time needed...**
**LAr temps might need to be watched more closely as much more dependent on timing.  **
******-source fairly weak for purity monitoring.**

## Final thoughts

**Last time things could settle before readout and got most of the charge from either the detector or from the calibration.  This time timing will matter much more crucially and will need to be tuned.**
**Cannot adjust the timing inside a tower i.e. see all possible capacitance variations**
**Cannot adjust timing below the crate level.  Fine-tuning (add cables length) could be done between the 6 crates in a quadrant. **

## Reserve

## Preamp Species

**14+1 (ICD) species of preamp **
**Feedback provide compensation for RC from detector capacitance and cable impedance**
**Readout in towers of up to 12 layers**
**0:EM1, 1:EM2, 2-5:EM3, 6:EM4, 7-10:FH, 11:CH**
**4 towers per preamp motherboard provides trigger tower (EM+ HAD) of **x **0.2 x 0.2**

| Preamp species | Avg. Detector cap. (nF) | Layer readout | Feedback cap (pF) | RC 
(ns) | Total preamps |
| --- | --- | --- | --- | --- | --- |
| A | 0.26-0.56 | EM1,2, HAD | 5 | 0 | 13376 |
| B | 1.1-1.5 | HAD | 5 | 26 | 2240 |
| C | 1.8-2.6 | HAD | 5 | 53 | 11008 |
| D | 3.4-4.6 | HAD | 5 | 109 | 8912 |
| E | 0.36-0.44 | CC EM3 | 10 | 0 | 9920 |
| F | 0.72-1.04 | EC EM3,4 | 10 | 14 | 7712 |
| G | 1.3-1.7 | CC EM4, EC EM3,4 | 10 | 32 | 3232 |
| Ha-Hg | 2- 4 | EC EM3,4 | 10 | 47-110 | 896 |
| I | —    | ICD | 22 | 0 | 384 |
|  |  |  |  |  | 55680 |

**Notes:**
Equal compensation
The integrating feedback cap is replaced with an RC circuit, which partially differentiates the output.
This counteracts the partial integration performed by the detector RC network (det. cap. plus cable impedance), giving the desired output of the original charge deposited in the detector.  Different caps in different parts of detector, hence different RC.
The open loop gain adjusting RC circuit helps pull out charge from det faster than the RC det network would otherwise allow

## Pulser Signal Shapes

**Calorimeter Signal at Preamp Input**

**Calibration Signal at Preamp Input**

**Calorimeter Signal after Preamp and Shaper**

**Calibration Signal after Preamp and Shaper**

**400ns**

**400ns**

**400ns**

**400ns**

- Response of calorimeter signal w.r.t. calibration signal < 1% at max. signal for variation of different parameters (cable length, Zpreamp, Zcable,...)
- No test beam running  absolute energy scale will have to be established from the data
- Maximum response time for EM and hadronic channels differ due to different preamp types.  Use delays and modeling to accommodate these
- Correct pulser response for different timings and shape
- Use initial “guess” based on Monte-Carlo sampling weights and Spice models of the electronics.

- Signal reflection

## Modeling the pile-up

- 320ns

**Duflot – QCD/Jet meeting Aug 17,2000**
**Crossing 396 ns**** ; ****peaking time 320 ns**** **
** ****Contribution of 3 crossings before **
** ****subtract previous crossing**** **

_**Total contribution:**_
-   100% mb(0)  + 36% mb(-1) + 9.7% mb(-2) + 2.4% mb(-3)
- - 100% mb(-1) - 36% mb(-2) - 9.7% mb(-3) - 2.4% mb(-4) =
-  100% mb(0) - 64% mb(-1) - 26.3% mb(-2) 7.3% mb(-3) - 2.4% mb(-4)

**Modeling the pile-up**

## Estimates of Noise Contributions

**Estimates of Noise Contributions**

**EM3 layer per cell**

****

**nF**

**GeV**

**GeV**

**GeV**

## Measuring Pulse Shape

**time**

**pulse**
**height**

**0**

**+6**

**+3**

**-3**

**sampling time with respect to trigger**

**increasing**** ****pulser delay**

-  scanning pulse shape by varying delay
-  max response obtained for different delay values in em/had channels:
-  to be taken into account for pulser pattern determination
-  different runs at different delay values necessary
-  instability in the relative timing at the high end
-  effect of BLS visible

**600 ns**

## Tevatron Timing Details