# Presentation: 172051

**HEBT, ring, & RTBT WS System**
**Preliminary Design Review**
**BNL, July 23, 2002**
**by Michael Plum**

***and Pete Cameron, CJ Liaw, Ross Meyer, John Power, Bob Shafer***

## Outline

**HEBT wire scanner system**
**Ring wire scanner system**
**RTBT wire scanner system**
**Responsibilities**
**Summary**

## Quantities & strokes

**All units will use same motion control as linac systems.**
- Phyton linear driver controlled by NI PCI card mounted in a PC.

| Location | Installed units | Stroke | Spares |
| --- | --- | --- | --- |
| HEBT | 11 | 8 inch | 2 actuators2 electronics |
| Ring | 2 | 8 inch | 1 actuator1 electronics |
| RTBT | 5 | 18 inch | 1 actuator
1 electronics |

## Signal processing & wire type

| Location | Method | Wires* |
| --- | --- | --- |
| HEBT | SEM
Same electronics as linac | 3 ea. 32 u dia. C |
| Ring | Beam loss
SEM backup method | 1 ea. 32 u dia. C |
| RTBT | SEM
Electronics now in conceptual design | 3 ea. 32 u dia. C, or
3 ea. 100 u dia. SiC |

- * wires offset so that no more than one wire at a time is within ±2 rms of beam center.

## HEBT wire scanners

**Beam pipe size is 5” OD**
**Actuators based DTL design, have slightly longer stroke ****(8” vs. 6”).****	**
- Custom design fabricated by Huntington.
**Electronics (actuator control and wire signal) same as for linac.**
- Biased wire, ac-coupled electronics.
- Linear stepper motor driver.
- Signal processor.
- PC.
**Calculation of wire temperature and signal strength.**
- Max wire temperature limited to about 1225 oC. Any higher and thermionic electron emission becomes significant.
- Assuming 1000 MeV, 26 mA avg. beam current, 0.10 x 0.15 mm rms beam, this will occur at about 900 us, 1 Hz, and at 110 us, 60 Hz.

## Huntington 6” stroke wire scanner assembly – cover removed

- signal wire
- vacuum connector

- micro
- switches

- ball lead screw
- support housing

- LVDT

- brake

- motor

- bellows

- fork

- carbon wires

- collet assembly

## Block Diagram

- Block diagram of the cards in the PC and connections to the electronics chassis, motor driver and wire scanner actuator.

- (Changing to
- Phytron linear driver)

## Linac signal processor chassis

- Front panel view of the 1U-high electronics chassis.  LEDs indicate power, wire status, gain setting, and B.I.T. state.  BNCs allow the user to monitor the analog voltage of each of the three channels, X, Y, Z as well as the timing source.

- Timing TTL monitor signal

- WS channel monitor ports

- Status indicators:  power, wire, gain, B.I.T.

## Driver module – all WS systems

**We plan to switch from the NI chopper driver to the Phytron CLD 20-24 linear driver motor. **

## Beam size in the HEBT

- From D. Raparia, 29/Apr/02.

## HEBT wire scanners (cont.)

**Estimate of accuracy of width measurement.**
- Smallest beam in HEBT is 1.1 mm rms.
- Assuming
- A wire positioning accuracy of 0.1 mm (same as expected for linac wire scanner actuators),
- Absolute signal error of 2% of peak (electrical noise)
- Relative signal amplitude error of 1% (non linearities)
- Negligible beam position and beam width jitter
- We expect to be able to measure the rms beam size with an accuracy of about 7%, including the difference between the rms of a beam and the sigma from a Gaussian fit.
- Resolution will be about 2%.

## HEBT wire scanners (cont.)

**Estimate of signal levels in HEBT. **
- Smallest signal is about 100 times less than signal at center of largest (4.3 mm rms) beam for lowest peak current (10 mA) beam. Computer model predicts **16 nA**.
- Largest signal is at center of smallest (1.0 mm rms) beam for highest peak current (38 mA). Computer model predicts **26 uA**.
- Allow factor of two error >> electronics should ideally be able to measure signals from **8 nA** to **52 uA** (in several gain stages).
- Present linac design can measurefrom 7.3 nA to 30 uA in 3 gainstages.
- Linac electronics may need slightmodification for higher input currents.

## Ring wire scanner system

**Beam pipe size is 8” OD.**
**Each actuator will have just one signal wire.**
**Total of two wire scanner actuators (one x, one y) in the ring.**
**Primary signal will be beam loss caused by the 32 micron diameter carbon wire.**
**Will also bring signals from wires up to equipment building.**
- Useful for measuring size of single mini pulse in ring.
- Wire will get too hot for SEM during normal operations.
- No plans to develop electronics specifically for the ring wires at this time.
- Will use HEBT or RTBT electronics and accept its limitations.
** **

## Ring wire scanner system signal levels

***                                                      ******Rough estimate***
***Wire in center of beam:***
- Assuming 32 u dia. C wire, cross section = 0.5 barns, 2.2 cm rms beam (largest size),
- there will be about
**7.3E-8 protons lost per circulating proton**.
***Compare to background beam loss:***
- Assuming 1 W/m uncontrolled beam loss, equal loss around ring circumference,
- there will be about
**8.9E-9 protons lost per circulating proton**
- in the 12 m of beam line near the loss monitor.
**Signal to noise is about 8:1 for wire at center of beam**.
- Will probably need signal averaging to get a reasonable profile.

## Ring wire scanner system time resolution

- Beam area A is approx. proportional to turn number n.
- A(n) = 0.0645 + 30.9 (n/1000)    [cm2]     (Liaw & Cameron, PAC 2001)
- Beam size is approx. x = sqrt(A)/
- % change per turn (1/x) (dx/dn)  1/(2n).
- Measurement around 100th turn must be made within 10 turns, or 10 us, to get a 5% measurement.
- Measurement around 200th turn must be made within 20 turns, or 20 us, to get a 5% measurement, etc...
**Loss monitor circuit and signal acquisition system must have time resolution of about 10 us or better, and a measurement accuracy of a few percent.**

## Ring wire scanner accuracy

**Estimate of accuracy of width measurement.**
- Assuming
- Smallest beam in ring is 2 mm rms
- A wire positioning accuracy of 0.1 mm (same as expected for linac wire scanner actuators),
- Absolute signal error of 10% of peak (electrical noise)
- Relative signal amplitude error of 3% (non linearities)
- Negligible beam position and beam width jitter
- We expect to be able to measure the rms beam size with an accuracy of about 10%.
- Resolution will be about half the accuracy.

## RTBT wire scanner system

**Beam pipe size is 8” OD.**
**New 18-inch stroke actuator design. Now working with Huntington on custom design. **
**Three signal wires per actuator.**
**32 micron diameter C wires, or 100 micron diameter SiC wires. **
**Take SEM signal off the wires. **
- Offset wires allows use of fast loss monitor as well.
**SEM signal processing electronics to be developed by John Power. **
- Now in conceptual design.
**BNL may also provide fast loss monitors to allow measurement of the beam profile with the beam loss method.**
**Wire heating calculations by CJ Liaw show a peak temperature of ****460 ****o****K**** for 2 MW beam (baseline is 1.4 MW). Wire heating is not a problem.**

## Beam size in the RTBT

- From D. Raparia, 29/Apr/02.

## Wire choice and signal levels

**Would like electronics to be linear from about 1% of signal due to wire in center of largest bunch with the fewest protons, to about twice the signal due to the wire in the center of the smallest bunch with the most protons. **
**About 0.23 to 7000 pC for SiC wire. Several gain ranges OK. **

|  | 0.032 mm dia. C | 0.10 mm dia. SiC |
| --- | --- | --- |
| SEM electrons per proton hitting wire, incl. circumference effect | 0.025 | 0.038 |
| Charge from 2E12 proton bunch hitting wire in center of 2.1 cm rms beam | 4.9 pC | 23 pC |
| Charge from 2E14 proton bunch hitting wire in center of 1.4 cm rms beam | 730 pC | 3500 pC |

## RTBT wire scanner accuracy

**Estimate of accuracy of width measurement.**
- Smallest beam in RTBT is 14 mm rms.
- Assuming
- A wire positioning accuracy of 0.3 mm (same as expected for linac wire scanner actuators),
- Absolute signal error of 2% of peak (electrical noise)
- Relative signal amplitude error of 1% (non linearities)
- Negligible beam position and beam width jitter
- We expect to be able to measure the rms beam size with an accuracy of about 7%.
- Resolution will be about 2%.

## RTBT wire scanner electronics design guidelines

**Use existing wire scanner/faraday cup systems electronics where possible**
- Standard rack mount PC
- Standard PCI data acquisition hardware
- Standard LabVIEW instrument control
**Modify existing WS analog front end to meet requirements**
- Modified gain and bandwidth (multiple gains)
- Modified calibration source current
- Common bias PS design
**Status: Now working on conceptual design.**

## Summary

**Plan to use same design as linac for the 8” actuators.**
**Now working with Huntington on the 18” stroke design.**
**Will use linac electronics for HEBT units. **
**WS system in ring will be based on beam loss with back up from SEM.  **
**WS system in RTBT will be based on SEM with backup from beam loss. Electronics now in conceptual design stage. **
**Designs are low risk, based on straightforward extensions to existing designs. **