# Presentation: 172056

**HEBT, Ring, & RTBT WS System**
**Update**
**BNL, March 26, 2003**
**by Michael Plum**

## Update summary

**Review committee last looked at these wire scanner systems on 23/Jul/02. **
**Responsibility for HEBT, ring, and RTBT wire scanner actuators and electronics officially transferred to LANL Sep/02.**
**Prototype 8-inch stroke actuator ordered Feb/03.**
**HEBT beam box design modified to keep wire scanner fork out of beam aperture, for all cases but one. **
- There is one location, in the HEBT arc, where the wire scanner fork will interfere with the beam pipe aperture. It has been deemed to be too expensive to fix this, so it was decided to live with it.
**Will start working on ring and RTBT layouts in April/03.**
**Data point on max wire temperature: carbon wires that support PSR stripper foil get up to over 1400 deg. C.**
**We are on track to meet our deliverables deadlines. **

## Quantities & strokes

| Location | Installed units | Stroke | Spares |
| --- | --- | --- | --- |
| HEBT | 11 | 8 inch | 2 |
| Ring | 2 (1 ea. H & V) | 8 inch | 1 |
| RTBT | 5 | TBD | 1 |

## 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.

## Pulse length limits and signal levels

| Location | Max beam pulse length | Peak signal |
| --- | --- | --- |
| HEBT | 900 us, 1 Hz110 us, 60 Hz[26 mA avg., 0.1 x 0.15 mm rms beam size] | 26 uA[38 mA, 0.1 x 0.15 mm rms beam ] |
| Ring | Rep rate and pulse length limitations TBD | N/A (beam loss measurement) |
| RTBT | No limit  | 730 pC   (32 u C wire)3500 pC (100 u SiC wire)[2E14 ppp, 1.4 cm rms] |

## Driver chassis and actuator

- Chopper driver chassis

- Linear driver chassis

- 6-inch actuator

## Linac signal processor chassis

## Committee observations

***Committee Observation – ******Wire breakage is a primary design concern.  Wire survival limits beyond 1225o C are not known. Carbon wires should not be planned for operation beyond this limit until more tests are done.***
**The 1225o C limit is just the temperature above which thermionic emission becomes a concern. The carbon wires that support the PSR stripper foil are in the beam all the time. From model calculations from CJ Liaw, these wires get up to 1410 oC during normal operation, and even higher during beam development periods. Also note that the melting point of carbon is over 3625 oC.**
**Other calculations by CJ predict max temperature of a 32 micron diameter wire in the SNS ring will be from 1960 oC (1 MW beam) to 2555 oC (2 MW beam).**
**While we can make a good case for operating at temperatures above 1225 oC, we cannot yet make a good case for wire survival during normal SNS ring operations. Now looking into profile measurements at reduced beam power and reduced rep rates.**

## Committee observations (cont.)

***Committee Observation – The advertised scanner resolution appears to be close to or beyond the state-of-the-art. ***
***Recommendation - ******It should be understood to what extent the machine operation and related studies would rely on this very good performance.***
**In the July 23, 2002 review we predicted we could reach a positioning resolution of 0.1 mm. **
**Since then we have measured the positioning accuracy of a 6-inch stroke actuator, and found the effective accuracy (it moves in two directions) to be ****0.11 mm****. The result for the 3-inch actuator was ****0.15 mm****. **[M. Plum, “SNS Position Accuracy Tests,” 31/Jan/03, SNS Tech Note 104050204-TR0001-R00]
**The required accuracy of the rms beam size measurement is 10%, and the required resolution is 5%. The positioning accuracy needed to meet this requirement is about ****0.3 mm****. **
**Given the above measured accuracies of 0.11 and 0.15 mm, I believe we can meet the 0.3 mm positioning accuracy requirement.**

## Time line

| Receive prototype 8 inch actuator and evaluate | Summer ‘03 |
| --- | --- |
| Receive prototype actuator for RTBT (stroke TBD) | Late Summer ‘03 |
| Receive production order of 8 inch actuators | Fall ‘03 |
| Receive production order of RTBT actuators  | Late Fall ‘03 |
| Design and fab forks | Summer ‘03 |
| Fab HEBT electronics | Summer ‘03 |
| Design and fab RTBT electronics | FY ’04 |
| Install HEBT actuators | Early FY ’04 |
| Install HEBT electronics | Mid FY ‘04 |
| Install ring actuators and electronics | Summer ’04 |
| Install RTBT actuators and electronics | FY ’05 |

- Note: BNL responsible for beam box design, fab, and installation.

## Summary

**Plan to use same design as linac for the 8” actuators (HEBT, ring).**
**Order for a prototype 8-inch actuator has been placed.**
**Fabrication of  linac electronics for HEBT units is underway. **
**RTBT actuator stoke will be limited by available beam tunnel space. Now working to determine maximum allowable stroke. **
**Designs are low risk, based on straightforward extensions to existing designs. **

## Slide 12