# Presentation: 859398

**D-plate**
**Final Design Review**
**Los Alamos, Mar. 14, 2002**
**by Michael Plum**

***and John Bernardin, Gerald Bustos, Steve Ellis, Matt Fagan, Bob Gillis, Jack Goia, Dave Ireland, Snezana Konecni, Ross Meyer, John Power, Dave Sattler, Bob Shafer, Jeff Wilkinson***

## Agenda

**Introduction -- M. Plum**
**Overview of the D-plate -- M. Plum**
**Mechanical systems -- R. Meyer**
**Beam stop -- S. Ellis**
**Slit thermal analysis -- S. Ellis**
**Electronic systems -- J. Power**
**Committee deliberations**
**Committee outbrief**

## Review Committee

**Bob Webber, Chairman, FNAL**
**Mike Borden, LANL**
**Jim Crisp, FNAL**
**Glen Decker, ANL**
**Ron Johnson, SLAC**
**Tom Powers, JLab**
**Marc Ross, SLAC (via e-mail)**

## Overall design review process

**Preliminary Design Review**
**Respond to committee observations and suggestions**
**Final design review**
**Respond to committee observations and suggestions**

## Final Design Review Process

**Evaluate design against design criteria and functional requirements**
**Items to for committee to address**
- Assumptions
- Relevant calculations
- Options considered
- Interface requirements
- Fabrication plan
- Actions taken from PDR to FDR
- Have the design criteria been met?
- Have the right analyses/ tests been done to support fabrication?
- Are there any “holes” from the PDR left unaddressed?
**LANL will consider committee’s feedback**
**LANL will respond to the committee’s written report**

## Charge to the committee

**Review the design**
**Categorize findings**
- Critical (potential “show stoppers”)
- Observations/ recommendations
**Consider key observations from audience participants**
**Give us an outbrief**
**Written report**

## Design review `scope

**Design Review Scope**
- D-plate mechanical design
- D-plate electronic design
- Interface issues
- Schedule
**Areas covered by other reviews**
- Beam stop engineering review held 6/Feb/2002

## Outline

**Overview of the D-plate.**
**Action items from the preliminary design review. **
**Physics requirements development.**
**Beam stop engineering review.**
**Radiation dose rates.**
**Interfaces.**
**Schedule.**
**Summary.**

## D-plate overview

- Quad

- Slits

- BPMs

- WS

- Harps

- View screen

- Energy degrader / Faraday Cup

- CM

- Beam stop

- 8 seg. halo scraper

- End of DTL tank 1

## D-plate overview

**D-plate overview**

** **

**D-plate takes position of DTL tank 2**

**Tank 1**

**Tank 2**

**2.5 Mev**

**22.8 Mev**

**Tank 1**

**Tank 2**

**Tank 3**

**Tank 4**

**Tank 5**

**Tank 6**

**86 Mev**

**36.57 meters**

**Drift tubes, Post couplers, and water system not shown for clarity**
**From ****John D. Bernardin**

**D-Plate Resides where Tank 2 is.**

**6.06 m**

## From the Preliminary Design Review...

**Recommendation – The outline Jim [Stovall] provided should be fleshed out, quantified, and detailed with a commensurate schedule to justify making time for the D-Plate in the commissioning scenario and to serve as realistic input to establish an integrated schedule for Linac commissioning. **
*Response – Done. E. Tanke is DTL commissioning leader. Plans are on line at *_[http://www.](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[sns](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[.](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[gov](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[/](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[projectinfo](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[/operations/commissioning.](http://www.sns.gov/projectinfo/operations/commissioning.htm)__[htm](http://www.sns.gov/projectinfo/operations/commissioning.htm)_
**Recommendation – ****Management should focus on [the systems integration and interface issues] to assure that the D-Plate engineering requirements and specifications are appropriate and that the D-Plate will be sufficiently exploited.  The D-Plate must not be considered in isolation.  Deliverables from LANL and from suppliers of supporting systems must be clearly defined. **
*Response – We are working closely with the physics, vacuum, water, and magnet teams to assure that the D-plate meets engineering and physics requirements. Also an Acceptance Strategy document has been written.  *

## From the Preliminary Design Review...

**Recommendation – ****Develop integrated schedule [that includes vacuum, water, I&C, power, ...]. [Add resources to vacuum and water effort.]**
*Response – Noted. To relieve pressure on existing resources, a contract engineer was hired to work on the D-plate water and vacuum. *
*Response – The D-plate vacuum and water needs have been incorporated into the integrated schedule.*

## From the Preliminary Design Review...

**Recommendation – Assembly and s****hipping methodology need to be carefully considered.  Communication between LANL and ORNL mechanical and installation groups needs to take place to resolve these issues at an early stage to avoid un-necessary costs...**
*Response – An Acceptance Strategy document has been written to clearly define roles, work, and responsibilities. Engineering and interface meetings are now held on a regular basis.*
*The plan is for LANL to check the components to ensure that they have been correctly fabricated and that they fit correctly to mating components. Final assembly and alignment will be done at ORNL. This process allows LANL to ensure a quality product and alleviates shipping concerns.*

## From the Preliminary Design Review...

**Committee Observation – ****It was not clear that the D-Plate has been specified consistently with all the beam measurements that need to be made from a beam physics perspective...  Not all requirements of D-Plate diagnostics are yet well defined... ****Recommendation – Carefully consider again the full range of measurements and beam modes for which each D-Plate subsystem is required to perform. **
*Response – We agree that ideally the D-plate specifications would follow from linac commissioning studies. However, due to limited resources in the physics team, and therefore lack of input from the team, some of the D-plate specifications had to be derived based on experience with other accelerators. The LANL physics team leader (J. Stovall) is well aware of the D-plate specifications. As physics resources become available more effort will be focused on the D-plate, hopefully in time to make any mid-course corrections that may be necessary. Also, a member of the D-plate design team (M. Plum) is also a member of the physics and commissioning team. This will help optimize input from physics team and refinement of the D-plate requirements. *
*Detailed commissioning plans utilizing the D-plate are now available (ORNL web site). Physics studies have modeled the emittance gear and its required accuracy *[D. Jeon, “Uncertainty in rms emittance from the slit/collector in the DTL Diagnostic plate”, SNS/AP Tech Note]

## View screen

**Usage scenarios**
- Used as first check of low intensity beam out of DTL.
- Back up for more complicated diagnostics (BPM, wire scanner).
- Gross check of beam position and beam size.
**Al****2****O****3****(Cr) screen**
- 12000 phot/MeV-proton*
- 1013 rad limit*
- 693 nm peak emission wavelength*
- 5 ms decay constant*
- Linear up to about 400 deg. C*
**One mini pulse (700 ns, 38 mA) produces**
- About a 45 deg. C temperature rise
- Enough light to saturate camera >> need neutral density filter
**Maximum beam parameters approx. 1 Hz, 8 mini pulses, 38 mA pk.**

- *W. Sellyey, “Some Physics Considerations for AHF Beam Profile Observation,” 23/Jan/02 + private communication

## Energy Degrader/ Faraday Cup

**Usage scenarios**
- Needed to set DTL tank phase and amplitude to within ±1% and ±1 deg.
- Essentially same as ED/FC in the DTL tank 1 beam box, but able to take higher beam power.
- Check results obtained with ED/FC in DTL #1 beam box.
**Requirements  **
- Measure phase scan for 26 mA peak currents for pulse lengths long enough to reach equilibrium (50 us).
- DTL tank 1 ED/FC good for 140 us, 26 mA, 10 Hz.
- D-plate ED/FC good for 180 us, 26 mA, 10 Hz.

## DTL tank 1 ED/FC phase scan 80 – 108 % of nominal rf amplitude

- From J. Stovall

## Wire scanner

**Usage scenarios**
- Used to check optics for emittance and beam stop tunes.
- Used as check of emittance change as function of MEBT to DTL match.
- Can also check beam position against BPM measurements.
**Requirements**
- Check optics >> beam size at wire scanner changes from x = y = 2.0 mm to x = 2.3 mm, y = 0.92 mm >> need accuracy of about 0.15 mm or 7.5%.
- Measure emittance changes of about 10% >> need to measure beam width to accuracy of 5%.
- Expected accuracy of wire scanner is 5%. (Assuming 0.04 mm jitter, 0.08 mm position error, or 0.09 mm effective error.)

## Wire scanner and MEBT to DTL match

**Beam size at the D-plate wire scanner as a function of the MEBT quad settings.**
**Horizontal profile provides a rough check of the MEBT to DTL match. **
**Vertical profile can provide confusing results.**

- D. Jeon et. al. SNS/AP Tech. Note 09, 7/Mar/01

## BPMs

**Usage scenarios**
- Check beam steering. Steer beam to beam stop.
- Check beam energy.
**Requirements**
- Steer the beam to the dump with accuracy of 2 mm >> 4-inch BPM accuracy should be better than 1 mm. Accuracy spec is 1% of aperture radius, or 0.5 mm.
- Check beam energy.
- E = mc2 (*)3 (c/L) t.
- BPMs on same Roscoe box should give 2 deg. phase accuracy at 402.5 MHz, or 26 keV, or 0.5% tank 1 energy gain.

## Emittance measurement

**Usage scenario**
- Used to measure beam emittance for low average current beams.
- Test MEBT to DTL match. (Emittance is minimized for the best match.)
**Physics requirements**
- Must measure emittance of beam after it reaches equilibrium and after ramp (about 30 us) >> must withstand 50 us beam pulses and have bandwidth of at least 40 kHz.
- rms in relative error in rms emittance should be less than 6%. [D. Jeon, 10/Jan/02]
- To achieve this accuracy slit and collector position uncertainty should be less than about 0.11 mm rms (assuming 0.04 mm beam jitter). [D. Jeon, “Uncertainty in rms emittance from the slit/collector in the DTL Diagnostic plate”, SNS/AP Tech Note; prvt. comm. 5/Feb/02 ]
- Slit will be on Huntington actuator, which has been measured to have a position accuracy of 0.07 mm.

## Emittance and MEBT to DTL match

**Emittance gear provides test of MEBT to DTL match. **
**Emittance resolution of about  6% is desirable. **
**Model simulations and actuator accuracy measurements predict a resolution better than 6%.**

- D. Jeon et. al. SNS/AP Tech. Note 09, 7/Mar/01

## Emittance harp electronic specification

**Collector harp electrical specification**
- Smallest signal is slit at 2 sigma beam position, wire at 2 sigma of resultant profile. Estimate 3 uA signal for 10 mA peak beam current.
- Largest signal is slit at center of beam, smallest resultant profile on harp. Estimate 120 uA signal for 26 mA peak beam current.
- 40 signal wires per plane over 2 cm gives 8 wires over ±2(rule of thumb for good accuracy). Also model calculation by Jeon show that this is adequate.
- To read out harp will use electronics developed by LBL for FES tests.
**LBL emittance harp electronics specifications**
- 32 channel, 2 MHz, 16 bit digitizer, 2 V full scale, 100 uA/V. One bit is 3.1 nA. Max is 200 uA.
- Range is sufficient for use on D-plate, but little room for error at the upper end.
- ORNL/Diag has assumed responsibility for the electronics.

## From the Preliminary Design Review...

**Recommendation – Consider electrically isolating the D-Plate beam absorber to provide an additional inexpensive beam intensity diagnostic.**
*Response – Good idea. We have modified our design to do this.*
*See presentation by Steve Ellis.*
**Committee Observation –**** ****Design of the emittance slit and energy degrader were not presented. It was claimed that they would be similar to existing LEDA hardware.  However, beam parameters are not exactly the same, therefore it would be desirable at least to provide simplified analysis of thermal load etc.  Emittance measurements are likely to be the most important contribution of the D-Plate.**
*Response – We agree. Thermal model calculations have now been performed and the design has been optimized for the D-plate. *
*See slit presentation by S. Ellis.*

## From the Preliminary Design Review...

**Recommendation – ****The D-Plate system, especially the beam stop, would benefit from a failure mode analysis effort. Beam stop analysis should consider worst-case beam spot and not just average ideal centerline case...**
*Response – We have studied the optics and identified the worst case scenario. The beam density can be up to 14 times higher than nominal if the quadrupole magnet is set improperly. We will have the control system monitor the quad readback current and shut off the beam if the current strays outside of nominal settings. Minor beam mis-steering will identified by the 8-segment halo scraper system, and gross mis-steering will be identified by monitoring the current difference between the upstream current monitor and the current intercepted by the beam stop. *
*An engineering review of the beam stop was held 6/Feb/02. The design was reviewed in detail, and found to be complete and conservative.  *

## Emittance tune (G = 1450 G/cm)

- Y

- X

- Slits

- Harps

- Beam stop

## Emittance tune (G = 1450 G/cm)

- Xmax = 42 mm
- Ymax = 20 mm
- Xrms = 19 mm
- Yrms = 8.9 mm

## Beam stop tune (G = 2020 G/cm)

- Y

- X

- Beam stop

## Beam stop tune (G = 2020 G/cm)

- Xmax = 47 mm
- Ymax = 45 mm
- Xrms = 21 mm
- Yrms = 20 mm

## Small spot tune (G = 1000 G/cm)

- Y

- X

- Beam stop

## Small spot tune (G = 1000 G/cm)

- Xmax = 38 mm
- Ymax = 4 mm
- Xrms = 17 mm
- Yrms = 1.8 mm
- 14 x more dense
- than beam stop
- tune.

## Results of beam stop engineering review

**“****Uniformly the review committee was very impressed with the effort of the design team and did not see any “show stoppers” that would require significant redesigns.” ****—**** KC**
**“****The basic design is sound and straight forward.  If successfully fabricated, it appears to have large thermal and structural design margins.” — JS**
**“****I did not see any shop stoppers in the D-plate beam stop.  I believe that the basic design is sound as is the analysis methodology.  The design team has done a good job.” — WF**
**“****Overall, I was impressed with the SNS beamstop thermal design.  The analysis was quite detailed and the results seem quite reasonable. The beamstop design/analysis team has done a thorough, technically competent job.” — SB**** **
**See advance material on web for full report.**

## From the Preliminary Design Review...

**Recommendation – Determine alignment requirements as soon as possible. Establish specifications and alignment procedures so that impacts on mechanical design may be addressed at the earliest opportunity. **
*Response – We now have a table of alignment requirements, and we are working with Joe Error at ORNL to optimize the laser alignment target placements. *

## Alignment requirements table

## From the Preliminary Design Review...

**Committee Observation – ****The committee was presented a block diagram for the water control systems that will be used throughout the SNS Linac and for the D-Plate.  No hardwire connection between the water systems and the Machine Protection System was identified on the diagram.****Recommendation – ****This obvious oversight must be rectified. **
*Response – There was a miscommunication at the D-Plate PDR.  The water cooling system is tied into the Machine Protection System...  ...the water cooling system PLC is tied into a Global Control System IOC, which is in turn, tied into the Machine Protection System (as well as other systems).*

## From the Preliminary Design Review...

**Committee Observation – ****There appeared to be confusion or lack of closure on the water pressure requirements for the D-Plate beam stop.****Recommendation – ****There is no reason the beam stop should drive special water system pressure requirements.  Design beam stop to use normal water system pressures. **
*Response – This issue has been resolved. The beam stop will use normal water pressures, and no extra pumps should be required. *
**Committee Observation – ****Calculations of vacuum load in the D-Plate system at full power were not presented. Is beam load taken into account? Transient pressure bursts might be important for operation at full power.****Recommendation – ****Consider whether it might be wise to do vacuum calculations to include the loading caused by the beam on the dump.  The loading will probably be addressed as “conditioning” as the beam power is increased during the initial operation of the system.**
*Response – Extensive vacuum calculations have now been performed, including beam loading, and the vacuum system originally planned is more than equal to the task.*
*See advance materials posted at the ORNL web site. *

## From the Preliminary Design Review...

**Committee Observation – ****The D-Plate drawing depicts a large diameter vacuum connection from the D-Plate to the Tank 1 interface.  The purpose of this was not appreciated by the committee and it was noted that the high conductance connection might increase the possibility that “bad vacuum” from the D-Plate might feed back into the DTL tank... ****Recommendation – Consider whether a lower conductance connection might not be preferred. **
*Response – The vacuum calculations mentioned above address this issue. No changes to the vacuum connections to the DTL tank will be necessary.*
**Committee Observation – ****There confusion was expressed as to what materials and design was needed for a Faraday cup and there was no specification provided for the energy degrader.**
*Response – The energy degrader and Faraday Cup were omitted from the review due to time limitations. However, the design is now complete, and a tech note is now available to describe the requirements and specifications.*
*See earlier presentation during this series of design reviews.  *

## Radiation dose rates due to beam stop

- Beam stop dose rates. Full power (11.7 kW) operation. From F. Gallmeier, 25/Jan/02.
- Dose rate outside 1 m concrete + 30 cm borated polyethylene = 0.06 mrem/h. (from *I.Popova)*

## Interfaces and responsibilities

**Interfaces have been defined and responsibilities have been defined and accepted. **
- Acceptance Strategy document.
- Minutes of interface meetings.

## Responsibility table

| System | Electronics & PVs | User interface |
| --- | --- | --- |
| Loss monitor | BNL Diag. | ORNL Diag. |
| BPM | LANL Diag.  | ORNL Diag.  |
| Wire scanner | LANL Diag.  | ORNL Diag.  |
| ED/FC – cup, bias
            – actuator | LANL Diag. 
Controls | ORNL Diag. 
ORNL Diag. |
| Current Monitor | BNL Diag. | ORNL Diag.  |
| Sl. & Coll. emit.  | LBL & ORNL Diag.  | ORNL Diag.  |
| View scrn – camera
                 – acquis.
                 – actuator | LANL Diag. 
LANL Controls
Controls | 
LANL Controls
Controls |
| Halo scraper | LANL Diag.  | ORNL Diag.  |
| Beam stop | LANL Diag.  | ORNL Diag.  |
| Water | Water group | Controls |
| Vacuum | Vacuum group | Controls |
| Magnets | Power supply grp. | Controls |
| Machine protect | Controls | Controls |

## Schedule

**Fabrication and rough assembly by mid to late summer 2002.**
**Ship to ORNL**
**Final assembly, alignment, and system tests at RATS building Jul to Sep 2002.**
**Installation and testing Oct – Dec 2002.**
**First beam expected spring 2003.**
**A detailed schedule has been developed by Saeed Assadi.**

## Summary

**Physics requirements have been firmed up.**
**Detailed commissioning plans are now available.**
**Engineering and interface meetings are now held on a regular basis.**
**Interfaces have been defined and responsibilities have been defined and accepted. **(*See, e.g., Acceptance Strategy document, minutes of interface meetings.) *
**A detailed testing and installation schedule is now available. **
**Detailed vacuum and water calculations are now available.**
**Beam stop failure analysis has been performed.**
**A beam stop engineering review found the design to be solid, conservative, and thorough. **
**Radiation calculations have shown that borated polyethylene should be added to the concrete shielding. **
**The D-plate system is on schedule for delivery in late summer. **