# Presentation: 540314

**SNS WS System **
**Preliminary Design Review**
**Los Alamos, July 17, 2001**
**by Michael Plum**

## Agenda

**Welcome and charge to the committee (Plum)  15 min.  **
**WS requirements, physics and interfaces for linac (Plum) 25 min. **
**WS requirements and interfaces for ring, RTBT (Cameron)  15 min. **
**Laser wire (Connolly)  30 min. **
**Wire heating (CJ Liaw)  15 min. **
**HEBT, ring, RTBT actuators (Jim Cullen)  30 min. **
**Ring, RTBT electronics (Al DellaPenna)  20 min. **
**Linac actuators (Ross Meyer) 40 min. **
**MEBT, linac, HEBT electronics (Chris Rose)  30 min. **
**Lunch (provided for review committee and outside visitors)**
**Committee deliberations**
**Committee out brief**
**Note: Must terminate video link at 12:15 Los Alamos time.**

## Review Committee

**Bob Webber / FNAL (Chair)**
**Marc Ross / SLAC**
**Tom Powers / JLab**
**Joe Preble / JLab **

## Design Review Process

**Evaluate design against design criteria and functional requirements**
**Items to address**
- Assumptions
- Relevant calculations
- Options considered
- Interface requirements
- Manufacturing/procurement plan
**Consider committee’s feedback**
**Respond in writing to the committee’s report**

## Charge to committee

**Review the design**
- Are the design requirements adequately defined?
- Is the WS system design at PDR status? (I.e., ready to build and thoroughly test prototype units.)
- Are the right analyses/tests being done/planned?
- Does the work from PDR to FDR (Winter `01) look reasonable?
- Are there “gaps” in the design?
- Are the interfaces defined, understood, and addressed?
**Categorize findings**
- Critical (potential “show stoppers”)
- Observations/recommendations
**Consider key observations from audience participants**
**Give us an outbrief**
**Written report**

## Linac WS system usage scenarios

**Commissioning**
- Measure beam profile and position for reduced duty factor beams(50 to 100 us at 1 Hz).  Distinguish between ramp and flat top.
- Check match of beam between linac sections (MEBT – DTL – CCL – SCL1 – SCL2). Need as many WS’s as possible for this measurement.
- Indirect measure of beam emittance.
**Normal operations**
- Profile measurements will not be possible during normal operations. The wire would not survive, and the beam loss would likely be unacceptable.
**Troubleshooting**
- Check of beam position and profile.
- Check matching.
**Development **
- Same as commissioning.

## Linac WS system usage scenarios (cont.)

**Example of beam size variations for a mismatched beam. **

- Profiles are at quadrupole centers.                                  From H. Takeda.

## Linac wire scanner count

**DTL – 5 ea.**
**CCL – 8 ea.**
**SCL – 32 ea. (May install a few less because of the empty cryomodule locations.)**

## Beam parameters for commissioning

| MEBT commissioning | 1 – 10 Hz; 1 to a few minipulses or 10 – 100 us overall pulse length, 20 – 30 us ramp; 10 to 60 mA peak (as measured during mini pulse); 300 ns to unchopped mini pulses. |
| --- | --- |
| DTL commissioning | 1 – 10 Hz; 1 to a few minipulses or 50 us overall pulse length; 20 – 30 us ramp, 10 to 60 mA peak (as measured during mini pulse); 300 ns to unchopped mini pulses. |
| CCL commissioning
 | 1 Hz, 1 to a few minipulses or 50 us overall pulse length, 20 – 30 us ramp; 10 to 60 mA peak (as measured during mini pulse); 300 ns to unchopped mini pulses. |
| SCL commissioning
 | 1 Hz; 1 to a few minipulses or 100 us overall pulse length, 100 us ramp; 10 to 60 mA peak (as measured during mini pulse; 300 ns to unchopped mini pulses. |
| Ring commissioning
 | 1 – 10 Hz, 1 mini pulse, 10 to 60 mA peak (as measured during mini pulse), 300 to 700 ns long single mini pulses. |

- * All beams are H–

## Beam parameters for normal operation

| Peak beam current | 38 mA averaged over 690 ns mini pulse (26 mA avg.). (Was 52 mA in original design.) |
| --- | --- |
| Mini pulse period | ~ 950 ns |
| Mini pulses per pulse | ~ 1000 |
| Pulse length | 1 ms |
| Rep rate | 60 Hz |
| Beam sizes | MEBT:	x = 1.3 – 3.4 mm, y = 1.0 – 2.8 mm (1 )
DTL:	x = 1.8 – 2.7 mm, y = 1.0 – 2.7 mm (1 )
CCL:	2.3 to 3.1 mm (1 , x and y sizes are same)
SCL:	3.1 to 3.6 mm (1 , x and y sizes are same)
HEBT:	x = 0.5 – 2.0 cm, y = 0.5 – 2.0 cm (1 )
Extreme sizes are about sqrt(5) times larger |

## Beam diagnostics design requirements

- The beam diagnostics design requirements are divided into three parts: minimum requirements, target requirements, and desired requirements.
- It is necessary to meet the **minimum requirements** to commission and tune the SNS facility at the most basic level. If the minimum requirements can not be met then fabrication and installation of the system should be reconsidered.
- It is necessary to meet the **target requirements** for smooth commissioning and operation of the SNS facility and for maintainability of the diagnostics system.
- The **desired requirements** provide further enhancements of the diagnostics system that would allow improved understanding of the beam dynamics or improved beam or instrument troubleshooting capability. These requirements should be considered only if they do not impact the reliability, cost, or schedule.

## Linac WS Design Requirements

- Requirements as defined in Design Criteria Document SNS_104050000_DC0001_R00; April 30, 2001.

- Note: SNS parameters list, SNS-100000000-PL0001-R05, May 2001, lowers the peak current to 38 mA, and the average current to 26 mA.

## Linac WS Design Requirements (cont.)

- Requirements as defined in Design Criteria Document SNS_104050000_DC0001_R00; April 30, 2001 (cont).

## Linac WS system design issues

**Electronics will be based on a PC platform, similar to platforms used in other diagnostics systems at SNS.**
**Choice of signal wire.**
- Carbon – good thermal properties, bad oblation properties.
- SiC wires – good thermal properties, bad conductivity.
- Tungsten wires – OK thermal properties, bad beam scattering properties.
- We will likely use carbon wires in DTL. We are still considering our options for the CCL and SCL.
**Signal wires will burn up if linac duty factor is too high. **
- Protection via CM measurements at beginning of linac.
- Protection via MPS that monitors when actuators are off their out limits.
**Self test features.**
- Circuit to monitor for signal wire conductivity (See Chris Rose’ talk).
- Circuit to inject test signal at electronics front end.
- Plot motor pulses issued vs. position readback for actuator mechanical test.

## Linac WS system design issues (cont.)

**Biasing.**
- We plan to bias the wires negatively to drive off the secondary electrons May need to change polarity for low energy operations, where H– particle is stopped in wire.
**Scan time.**
- Scanners will primarily be used at 1 Hz beam rep rate. For about 30 data points, plus overhead, need about 40 seconds per scan with no averaging. Need a couple minutes with averaging.
**Halo measurements.**
- May be possible depending on signal levels, beam energy, background noise, etc.
**Qualification tests.**
- Failure of the SCL wire scanner has particularly high consequence. The prototype actuator unit will be carefully tested for particulates, ruggedness, and cycled for about 8,000 times.
**Project Change Request approved June 2001 calls for two signal processors per PC platform to save $$$.**

## Signal Level Estimate

## Interfaces

**The electrical interface occurs at the rack (except for pickup cables) where the electronics are mounted. I/O from the RTDL / event link, Ethernet, MPS, 120 Vac on/off.**

- Network attached
- instrument

- WS actuator

- IP

- RTDL

- Event link

- Ethernet
- Channel Access

- Machine protect

- Application programs

- 120 Vac on/off

- Control system

## Interfaces (cont.)

**The mechanical interface occurs at the beam pickup flange or weld joint. **
**Example of mechanical interface definition for the CCL wire scanners (taken from the DCD).**

## System responsibilities

**Saeed Assadi, responsible  for ORNL portion of project.**
- Acceptance of WS systems and integration into SNS project.
- Oversight of installation and testing.
**Mike Plum, responsible for LANL portion of project.**
- DTL, CCL, SCL actuators.
- Linac electronics. (Same electronics design will be used for MEBT and HEBT).
- LANL may become responsible for HEBT, ring, and RTBT actuators.
**Pete Cameron, responsible for BNL portion of project.**
- MEBT, HEBT, ring, RTBT actuators.
- HEBT, ring and RTBT electronics.
**Larry Dolittle, responsible for LBL portion of project.**
- MEBT electronics.
**Responsible parties will work together to develop a handoff strategy and agree on the criteria that define a successful system handoff.**

## Schedule

**Plan to have electronics design complete by fall 2001 so it can be used by LBL for MEBT commissioning. **
**First deliverable for LANL is DTL tank 1 wire scanner actuator and electronics, and D-plate actuator and electronics, approx. Nov. 2002. **
**Last deliverable is the SCL actuators and electronics, now scheduled to be around summer 2004. **

## Summary

**We are on track to deliver, on schedule, a WS system that meets all target requirements.**