# Presentation: 556658

## Progress on Profile Monitor SEM’s

- Beam Test results from MiniBoone
- Bias foil
- Resolution studies
- Delivery of First Production SEM
- Vacuum Tests
- Actuator Tests
- What needs to be done here at FNAL
- Production Outlook

- 10 cm Beam Port

- Signal Feedtrhroughs

- 9cm OD Bellows

- LVDT

- Stepper Motor
- & Linear Slide

- Limit Switch

- 25cm Ø Conflat

- Beam-intercepting Ti foils (5m)

## Beam Test in MiniBoone Transfer Line

- Two study periods:
- Fall ’03 long term data collection during normal MiniBoone running
- March ’04 repeated bias foil study

**Bias=0Volts**

**Bias=100Volts**

## Bias Foil Data

- Repeat study at several beam intensities
- Each point is a single shot, so fluctuations possible
- Vertical scale is pulse height on all SEM strips divided by Toroid intensity (normalize to 1.0 at 100V and lowest intensity)
- Reasonably good evidence for utility of the bias foil.

## Resolution Studies

- Over 50K spills from last Fall
- Could study resolution one of two ways:
- Hope beam stable at one position, measure deviation of reported position from SEM
- Allow spills where beam is moving around, try to correllate with BPM nearby (VP871)
- Two quantities to estimate centroid from SEM
- Pulse-height weighted mean strip number
- Fitted mean strip using assumed gaussian profile of beam.

## An Example of Looking for Stable Beam

- Run numbers correspond to MB-supplied runs
- Look visually at this plot, take projections over several spill ranges
- Approximately 5 such runs we looked at

- Generally observe fitted SEM position worse spread than weighted mean
- Generally SEM is smaller spread than BPM

## But is Beam Ever Truly Stable?

- Over some spill ranges spread is more like 150m, others (here) closer to 90m
- Does variation come from
- Beam moving over course of our projection
- Intensity?
- Comparing spreads when beam hits different location on our SEM (recall strips probably not perfect!)

## Comparison of Several Periods

| Run/spill | Weighted SEM pos. Spread (m) | Fitted SEM pos. Spread (m) | Vertical Position on SEM (mm) | BPM spread (m) | Beam Intensity (1012 ppp) |
| --- | --- | --- | --- | --- | --- |
| 643/
16000-18000 | 93 | 89 | -0.12 | 127 | 4.7 |
| 643/ 10000-15000 | 145 | 147 | -0.6 | 158 | 4.6 |
| 643 / 2200-5500 | 158 | 180 | -4.5 | 189 | 4.6 |
| 641 / 16300 – 18100 | 111 | 131 | -4.8 | 137 | 4.7 |
| 641 / 12800 – 14300 | 136 | 146 | -2.4 | 162 | 3.9 |
| 641 / 7000 – 8700 | 154 | 155 | -0.5 | 158 | 4.6 |
| 640 / 5600 – 7000 | 136 | 141 | -1.0 | 150 | 4.6 |
| 640 / 4200 - 5600 | 126 | 134 | -1.5 | 143 | 4.6 |
| 640 / 1000 - 2900 | 131 | 142 | -1.3 | 150 | 4.6 |
| 639 / 1500 - 3000 | 112 | 124 | -4.2 | 135 | 3.9 |

- Best guess if presume beam movement is culprit

## Correlate with BPM?

- Impression is that SEM resolution smaller than BPM?
- Residuals fold in BPM+SEM resolutions
- If assume *equal* SEM, BPM resolutions then SEM ~ 85 m.

*Run 639, spills 7500 – 14000*

## Another Time Period to Correlate with BPM

- Similar (maybe a little better?) results
- Different location on SEM
- Similar spread of beam over SEM (3mm)

*Run 642, spills 0 – 11800*

- Still lingering impression that SEM, BPM, ’s are not equal

*Run 640, spills 11900 – 16000*

## Thermal Simulations

| Material | T (°C) (5m foil) | Fractional Elongation (10-4)   (5m foil) | Dynamic Stress (MPa)     (5m foil) | Yield Strength (Mpa) |
| --- | --- | --- | --- | --- |
| Be | 64 | 0.92 | 188 | 240 |
| C | 186 | 0.25 | 19 | 469 |
| Al | 138 | 2.9 | 238 | 35 |
| Ti | 222 | 1.1 | 208 | 220 |
| Ni | 264 | 4.6 | 736 | 1580 |
| Ag | 449 | 5.4 | 709 |  |
| W | 715 | 2.5 | 1305 | 550 |
| Au | 729 | 7.1 | 807 | 205 |

- Thin foil strip heats less than wire
- Larger surface/volume ratio
- More  rays escape (lower *dE/dx*)

- Input *dE/dx* for 120GeV protons (restricted *E* loss *dE/dx*[*T*e<*T**cut*])
- Cooling assumes blackbody radiation, thermal cond. to ends of foil/wire

## First SEM Delivery

- HV Foil

- “Beam Out”
- Position

- Accordion
- Springs

- Halo Foil

- Signal Strips

- Signal Cables

- “Beam Hole”

- Recall cables on this paddle are different from future models
- Signal lines routed through shaft
- We changed partially to reduce vacuum gas load (this now suspect)
- We will maintain full ‘swapability’

## Foil Etching

## Foil Insertion Actuator Tests

- Tested with chamber evacuated to 1E-8 Torr on turbo pump
- Similar short-term ~1m accuracy as observed last fall on bench test
- Slightly worse performance if no vacuum (5–10 m) so vacuum helps slow motor
- Long-term study would be helpful once we get FNAL controller driving this.

*Final Position (****m)*

*Trial Number*

- 4m

*Approximately 16 hrs.*

## Vacuum Tests of SEM#1

- Rate of pressure rise is 9E-9Torr/sec
- Volume is ~ 14.9 liters
- Infer outgas rate 1.3E-7 Torr-liter/sec (could be O-rings?)
- Ultimate pressure on ion pump ~4E-9Torr
- Infer pump speed at chamber is 35 liter/sec (consistent with 50l/sec pump and the conductance of cross, gate valves, *etc*)

## Vacuum Tests (cont’d)

- RGA test performed with SEM gated in/out of system
- Largely similar contaminants as obtained last fall.
- Evidently a very small leak (virtual??) exists – O-rings?.

## What’s Not Completed on SEM #1

- Brackets not anodized
- No plexiglass moisture cover
- Plexiglass cover also will have feedthroughs for
- LVDT
- Motor
- Switches
- Signal lines
- HV
- When we bring this cover up, will bring cables to go from vacuum feedthrough to plexiglass feedthrough.

## What Needs to be Done at FNAL

- Cary K. to disassemble 10” CF flange seal
- Survey / alignment of foils
- Optical!
- With respect to dowel holes on 10”CF, moving shaft
- Re-bake of SEM for vacuum
- Requires removing actuator
- Requires jig (supplied) to stabilize bellows during bake
- Re-assembly of actuator
- We would like to do this (lots of concern over alignment of bellows, which affects fatigue lifetime)
- We will supply plexiglass cover at this time

## Production

- All vacuum chamber parts complete
- Now cleaning all parts
- So far 6/12 cans clean
- Paddles+shafts all through “1st pass” clean (soapy water)
- Yet to commence
- 10” CF lids
- small accessories

## Production (cont’d)

- New kapton ribbon cables have arrived
- Checked one in vacuum chamber – no problems
- Tested flexing using actuator + paddle mounted on 10”CF

## Production (cont’d)

- Will assemble all 1mm pitch paddles simultaneously
- Commence next week – total time ~ 3wks
- Implies next bakeout *not* before May 8
- Actuators
- Require some revision based on 1st SEM
- Re-design commences May 8
- Require 4wks to machine all parts
- 0.5 mm pre-target SEM’s
- Ceramic designed
- Paddle frame still tweaking
- Foil tests seem slow at vendor (limited by our 1mm jobs?)