# Presentation: 402125

## Beam in Gap Data Acquisition R. L. Witkover

## Action Items from July 2002 Review

- There is concern that the BIG measurement can be calibrated to the 20% resolution level
- The concern is justified. But we believe that the 20% calibration accuracy is possible.
- Loss studies still need to be done modeling the calibration technique.
- Monitoring the losses with a fast detector at a single point will not detect the total kicked beam loss but it may provide a proportional measure.
- Note that the final measure of the BIG efficiency would be how much beam hits the extraction kicker during the gap time. An additional gated PMT should be located viewing the kicker to monitor this.

- SNS BIG DAQ

- March 26-27, 2003

## BIG Measurement Approach

- Limiting apertures are the collimators
- Locate detector near collimators (Further study needed)
- Collimators designed to intercept controlled losses
- Beam cleaned from gap will be lost in collimators
- In place all the time – allows measurement during normal operation
- Will be “warm” area – possible high background which may make fine measurement difficult
- Beam Halo measurement scraper can be used for higher resolution BIG measurement
- Becomes temporary limiting aperture
- Lower background region
- Cannot be used continually – losses to high
- Use both approaches

- SNS BIG DAQ

- March 26-27, 2003

## Loss Distribution Near Collimator

- SNS BIG DAQ

- March 26-27, 2003

## The Problem

- Estimate of Controlled Losses at the Collimator
- Loss during bunch but may be significantly more during commissioning or studies, saturating detector
- Gate detector off during bunch to keep from saturating

| Source | Fraction |
| --- | --- |
| Beam In gap | 1.0x10-4 |
| Excited H0 at foil | 1.3x10-5 |
| Space Charge Halo | 1.9x10-3 |
| Energy Straggling at foil | 3.0x10-6 |

- SNS BIG DAQ

- March 26-27, 2003

## Gated Photo-multiplier Tubes

- SNS BIG DAQ

- March 26-27, 2003

## Detector

- Several gated high gain, high speed detectors available
- Hamamatsu H7680/-01
- Gated Photo-multiplier
- 5 x 104 gain swing
- 1.7 ns rise time
- Solid state gating and HV ps in unit (in tunnel)
- Hamamatsu R5916U-50
- Gateable Micro-channel plate
- 108 gain swing
- 0.18 ns rise time
- Leaning towards Micro-channel plate

- SNS BIG DAQ

- March 26-27, 2003

## Wideband Amplifier for FBLM

- SNS BIG DAQ

- March 26-27, 2003

## Data Acquisition

- With < 300 nsec gap, need high sample rate ADC to acquire signal, such as:
- Dedicated 1 GSa/s scope under Labview control .......Very expensive
- BCM/BPM PCI card with 80-100 MSa/s ADC...Requires development
- Commercial PCI Fast ADC module
- Acquiris (Module under test at ORNL)
- DP-105	0.5 GSa/s,    8-bit  1 Mb      = 150 samples
- DP-110	1.0 GSa/s,    8-bit   2 Mb     = 300 samples
- DP-210	2.0 GSa/s,    8-bit   4 Mb     = 600 samples
- CompuScope 82G (Gage-Applied) – 2GSa/s, 8-bit = 600 samples
- 100 MHz BW, 400 MSa/s, 8-bit = 125 samples
- 	Unit to be determined by BNL-SNS Controls Group

- SNS BIG DAQ

- March 26-27, 2003

## Calibration

- _Technique_
- Inject 1 turn (0.1% of full beam)
- Execute resonant gap cleaning during the beam pulse
- Measure turn-by-turn change in total charge with BCM
- Measure losses at the collimator (or Halo Scraper), turn-by-turn, over kick duration
- Measure change in total intensity, turn-by-turn, over kick duration
- Need AP studies to estimate accuracy of the measurement
- Can 20% be achieved?
- Relative measurement still important
- Estimate of cleaning efficiency can also be made by locating a Gated PMT at Extraction Kicker.
- Measure loss at Extraction Kicker during gap with BIG cleaner Off and On.

- SNS BIG DAQ

- March 26-27, 2003

## Summary

_** **_

- Need to purchase and test samples of Gateable  PMT-MCP
- Need to coordinate purchase and test of fast PCI ADCs with ORNL
-  Further simulation and analysis needed for
- Losses caused by Halo scraper due to BIG kick
- Losses at collimator due to BIG kick
- Loss pattern at Extraction Kicker during extraction

- SNS BIG DAQ

- March 26-27, 2003