# Presentation: 469599

## NSLS-II Accelerator System  Advisory Committee Review 

**Diagnostics Design and R&D**
**Om Singh – Group Leader **
**July 17-18, 2008 **

## Outline   

- SR Diagnostics Hardware  -- Layout & Locations
- RF BPM Resolution Requirements – Various time scale
- Standard RF BPM
- Insertion Device RF BPM
- RF BPM Electronics Evaluation
- Pin-hole Camera Resolution Simulation
- Near Term Plan
- Summary

## SR Cell Diagnostics Systems – BPM & Beam Loss Monitors 

**SR Cell Diagnostics Systems – BPM & Beam Loss Monitors **

- 3PW or BM B-Line

- BPM

-              SC               FC                   FC                            FC                      FC             SC

- BPM

- BPM

- BPM

- BPM

- BPM

- BPM

- BPM

- A) Standard Gap RF BPM  6 per cell

- B) Small  Gap RF BPMs   2 or 3 per Cell; Button Assembly on a Stand or ID Chamber

- D) Slow & Fast
-  Correctors

- C) X-ray BPMs – up to 2 / FE

- ID Beamline

- E) Beam Loss monitor (Location TBD)
-       p-i-n diode detector ; 2 per cell
-       scintillation detectors; 10 total
- F) RF PUEs  2 total for top-off

## SR Diagnostics Hardware Locations - Preliminary 

| Location | Hardware |
| --- | --- |
| Cell 22 - 3PW | Diagnostics Beamline – 
X-Ray pinhole |
| Cell 24 - BM-A | Diagnostics Beamline –
zone plates imaging |
| Cell 26 - 
3PW location | 1 short stripline – 0.15 m |
| Cell 28 -
3PW location | 1 short stripline – 0.15 m |
| Cell 30 –
BM-A Source | Diagnostics Beamline –
Visible Synch. imaging |
| Cell 30 –
CH2S2A location | Vertical Scraper # 2 |
| Cell 30 –
Up of P3S4A BPM | Horizontal Scraper # 2 |

| Location | Hardware |
| --- | --- |
| Cell 1 (or 29) –
Up of P3S4B BPM | Horizontal Scraper # 1  |
| Cell 1 (or 29) –
3PW location | Vertical Scraper # 1 |
| Cell 7 - 
Upstream of ID | 1 Long stripline – 0.3 m |
| Cell 11 -
Upstream of ID | 1 Long stripline – 0.3 m
1 DCCT – 0.3 m |
| Cell 27 –
3PW location  | 1 Short stripline  |
| Cell 29 –
3PW location | 1 Short stripline  |

**Odd Cells                                   Even Cells**

## NSLS-II Lattice Functions & Electron Beam sizes / divergences 

| Types of source | 8.6m ID  | 1-T 3-Pole wiggler | Bend magnet | 6.6m ID |
| --- | --- | --- | --- | --- |
| x  (μm) | 108 | 175 | 44.2 | 29.6 |
| x’ (μrad) | 4.6 | 14 | 63.1 | 16.9 |
| y   (μm) | 4.8 | 12.4 | 15.7 | 3.1 |
| y’ (μrad) | 1.7 | 0.62 | 0.63 | 2.6 |

***NSLS-II Lattice Functions & Electron Beam sizes / divergences ***

- Lattice
- Functions

- Electron Beam Sizes
-  & Divergences

- Most challenging
- Beam stability
- Requirements
- = ~ 0.31 μm

## NSLS-II SR RF BPM System – Performance Requirements* 

| Parameters/ Subsystems |  |  |  | Conditions | Standard RF BPM System Resolution Requirement |  |
| --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  | Vertical | Horizontal |
| Single bunch, Single turn resolution 
(@ 378 kHz) |  |  |  | 0.05 nC charge   | 500 μm rms  | 500 μm rms  |
|  |  |  |  | 5.0 nC charge | 20 μm rms  | 20 μm rms  |
| Single bunch stored beam resolution 
(0.017-200 Hz BW) |  |  |  | 0.02 mA current   | 10 μm rms | 10 μm rms |
|  |  |  |  | 2.0 mA current | 1 μm rms | 1 μm rms |
| 50 mA ***  to 
500 mA 
Stored beam resolution – 20% to 
100 % 
duty  cycle | BPM 
Receiver
Electronics | Assuming no contribution from bunch/ fill pattern effects |  | **0.017 Hz to 200 Hz  | 0.2 μm rms | 0.3 μm rms |
|  |  |  |  | 200 Hz to  2000 Hz | 0.4 μm rms | 0.6 μm rms |
|  |  |  |  | **1 min to 8 hr drift | 0.2 μm pk-pk | 0.5 μm pk-pk |
|  |  | Bunch charge/ fill pattern effects only |  | DC to 2000 Hz  |  0.2 μm rms | 0.3 μm rms |
|  | Mechanical  motion limit at  Pick-up electrodes  assembly 
(ground & support  combined) |  | Vibrations | 50 Hz to 2000 Hz  | 10 nm rms | 10 nm rms |
|  |  |  |  | 4 Hz to 50 Hz   | 25 nm rms | 25 nm rms |
|  |  |  |  | 0.5 Hz to 4 Hz | 200 nm rms | 200 nm rms |
|  |  |  | Thermal | **1 min to  8 hr   | 200 nm pk-pk | 500 nm pk-pk |

- * Requirement values are preliminary  -  work in progress
- ** ID BPM system resolution values will be smaller ( factor of ~ 0.5)
- *** @ 5 mA – 50 mA stored beam, BPM receiver resolution values will be worse (factor of ~2)

- (Req. met - Test Data Later)

## BPM Evaluation - Baseline Design

- Baseline Design (one button/flange)
-   Consists of one 10 mm dia. button w 34 mm flanges
-   ~ 28 mm horizontal separation & ~ 25 mm vertical aperture
-   Matlab Simulation  input power level @ 500 mA= - 2 dBm (OK)
-                                      Sx =~ 0.12 / mm ; Sy =~ 0.04 / mm (low)
-   Electronic Resolution in frequency band 0.017 – 200 Hz
-              H-Resolution =~ 100 nm  ;  V-Resolution =~ 300 nm

-  Baseline Design (28x25)

- SX=~0.12

- SY=~0.04

## BPM Evaluation - Proposed Design

- Proposed Design
- (two button/flange)
-  Consists of two ~7 mm dia. buttons on a single 50 mm dia. Flange; with ~16 mm H-separation (vertical aperture remains same - 25mm)
- Two buttons on a flange reduces total flange counts & makes survey/ alignment process easier
-  7 mm button (over 10 mm) is also favored for beam heating issue

## BPM Evaluation - Proposed Design (cntd)

- Proposed Design (two button/flange)
-   Matlab Simulation shows
-      input power level @ 500 mA = -8 dBm (OK)
-       Sx =~ 0.09 / mm ; Sy =~ 0.09 / mm (OK)
-   Electronic Resolution in 0.017 – 200 Hz BW
-        H-Resolution =~ 135 nm
-            V-Resolution =~ 135 nm (200 nm reqd)

- Resolution vs Input Power

- -8 dBm

- Resolution

- SX=~0.09

- SY=~0.09

## Flange Layout – 7mm buttons

##  RF BPM Button

**Findings, recommendations and comments:**
-  Button block cooling issues should be addressed, including block distortion and the possible compromise of Helicoflex flex gasket integrity due to beam heating from trapped modes (Diamond experience).
-  A smaller button diameter should be considered to reduce button heating and impedance (look at the ALBA paper submitted to the 2007 DIPAC).

**NSLS-II Accelerator Technical Review **
**Instrumentation and Diagnostics**
**August 9-10, 2007**
**Report of the Review Committee**
- submitted September 28, 2007

-  Button Heating

## RF Button Heating Mini-Workshop at EPAC (June,2008)

-  Organized by Soleil/NSLS-II  - attended by experts from NSLS- II, KEK, Soleil, Diamond, PEP-II, ESRF, PETRA-III, SLS, SPEAR3, Bergoz & Others.
-  Presentations from NSLS-II, Soleil, Diamond, ESRF
-  Measured temperatures of connector pin on ambient side
-  in the range of 60oC @ ESRF
-  in the range of 100oC @Diamond
-  suggesting buttons themselves may be considerably hotter (~ several hundred oC)
- Estimated power at Diamond (from both GdfidL and temperature measurements) is ~5W/button, distortions/ position drifts are large ~10 microns
- Scaling to NSLS-II parameters suggests to do initial Ansys analysis with ~3W/button

## RF Button Heating mini-Workshop at EPAC (June,2008) (cntd)

- Agreement on mechanism of heating – hi Q trapped mode in transmission line formed by outer circumference of button and inner surface of housing.
- Diamond results suggest - do initial Ansys analysis with 3W/button to get thermal distribution/distortion – this is in progress
- Soleil simulations suggest - adjust button thickness and gap to wall to change transmission line impedance
- Gdfidl simulation - Kloss factor    as thickness
- 0.012 V/pc @ 2 mm; 0.007 V/pc @ 5mm
- Repeat the analysis with “Microwave Studio” simulation
- Ongoing communication/collaboration with other labs

## ID BPM Button  - Baseline Design 

-  Baseline design provides adequate sensitivity – SX=0.26; SY=0.14
-   Detail button heating analysis needs to be done with NSLS-II beam
-   Two configurations of ID BPMs are proposed
- Normal configuration - uses a low thermal expansion stand for stability
- Alternate configuration – buttons mounted on ID chamber, when
-    adequate space is not available for bellows, transitions and stand.

- Established Design – used at APS & Elettra

- Two 4 mm Dia buttons
- HS = 10 mm

- Flanges mounted on top & bottom of Small gap Chamber

## Sensitivity Optimization – Rotated Flange 

- Vertical sensitivity will be further optimized by rotating the 2-button flange, if needed
- Effects of longitudinal displacement of buttons needs to be analyzed

-     Rotated                                 Un-Rotated

- Sensitivity vs H-separation

## Calibrator Set-up

-  Confirm transfer function calculations
- Use *single wire *to simulate beam current; mounted on two motor controlled assemblies.
- Use two 34 mm dia. flanges; mount on a large flange to adjust H-separation by rotation
-  Explore interaction between beampipe modes and button resonance
- Evaluate BPM electronics
-  Develop beam simulator – Possible Collaboration with SLAC
-  Evaluate position and fill pattern dependencies – critical for top off operation

## ID-BPM Stable Support   

- 10” Dia Carbon fiber composite
-  stand limits thermal expansion
-   to 20 nm/m/0.1oC

- BPM assembly –
-  has 3 invar rods for alignment
-  small gap vertical aperture & 4 mm
-    dia buttons for optimizing sensitivity
-  Standard size flange at each end

- Specification  Total Thermal
- expansion < 100 nm

- R. Alforque

## ID BPM Support Thermal Stability

-  Position Stability Requirement for User BPMs is 100nm vertical
-  Temperature stability spec for the tunnel is +/- 0.1C
-  Need to verify that support post meets spec
-  Build a fiducial structure using additional low TEC posts (next slide)
-  Thermally isolate the fiducial, and give it lots of mass ( ~ 1 week)
-  Thermally isolate the test post, use heaters to vary temperature ( ~ 1 hour)
-  Use capacitive and DVRT sensors to measure length variations
-  Status
-  DAQ, some position sensors, and some temperature sensors in house
-  POs for remaining position and temperature sensors have been written
-  Shop fabrication of the test stand is underway

## ID-BPM Support Test Set-up

- Notes:
- All components to be wrapped with insulating blankets wherever possible
- 2. 3/16” sstl rods in tension will support the central tube
- 3. All materials sstl other than the carbon fiber tubes
-          Indicates Pt temp sensor
- 	    Indicates TC temp sensor

**ID-BPM Support Test Set-up**

**at both ends** **measure relative displacement due  to temperature variation**

## RF BPM Electronics -Proposed Studies

- Long term stability (for centered and off-centered beams)
- Measure dynamic range
- Dependence on ambient temperature
- Fill pattern dependence (including different envelopes)
- Dependence on RF frequency
- Effects of cable length mismatch
- Noise spectrum
- Explore for “dangerous” frequencies
- Signal pre-processing
- Establish acceptance test requirements

## Stand for Stability Test for Libera Brilliance

- Libera Brilliance

- Attenuator

- A

- B

- C

- D

- 4-way
- Splitter

- Gated
- Oscillator

- Func.
- Generator

- Attenuator

- Attenuator

- Attenuator

- system clock

- machine clock

- 500 MHz

- Reference   10 MHz

- External Clock

- Repeater

- RF frequency can be modified by external clock
- Chosen configuration provides phase locking between carrier and beam envelope
- Arbitrary waveform generator - provides amplitude or phase modulation/ trigger pulse modulation
- Temperature is monitored with platinum PT-100 probe using Digital Multi-meter

## First Results from the Libera Tests – Meet Drift Spec.

- TEMP
- ~ 1 oC

- HOR
- ~ 200 nm

- VERT
- ~ 100 nm

- TEMP

- HOR

- VERT

-   7 Hrs

- Power level 6 dBm (0 dBm at each input)
- 80% fill (2 μs pulse duration with 2.62 μs pulse repetition rate)
- Temperature Drift 200 nm /°C

## Pinhole Camera with 3PW Source

- 3PW has higher magnetic field (1.14 T) than dipole. Shorter critical wavelength provides better spatial resolution. Large vertical β-function (21 m) gives large beam size (12.4 μ). Horizontal beam size is defined predominantly by energy spread (σE/E·η=170μ) rather than emittance (1nm·4.1m)1⁄2=64μ. Attenuator reduces heat load on elements and serves as high pass filter for synchrotron radiation.
- Estimation of resolution is done using MATLAB script.

- Achievable resolution of 5.2 microns is sufficient for reliable measurement of vertical beam size (12.5 microns for 8 pm emittance)
- Image of the beam is magnified by factor 5 and loss of resolution due to phosphor is of less importance)

## Near Term Plan 

-  Complete detail RF button heating analysis
-  Prototype two-button/flange BPM & test
-  ID-BPM support procurement in process
-  Design & build test set-up to measure support
-     thermal stability
-  Integrate & test BPM calibrator set-up with computer control
-  Develop program to evaluate/ compare BPM electronics

## Summary

-  Location of bpms and diagnostics hardware have been identified
- SR BPM resolution requirement table vs time scale in progress
- New button design in progress for standard RF BPM
- Heat issues are being addressed for standard & ID BPMs (RF)
- ID-BPM support design is complete; Procurement is progress
- ID-BPM support thermal test set-up designs in progress
- ID-BPM calibration test set-up complete; Integration to follow
- Pin-hole diagnostic beamline design analysis in progress
- Near term plan has been identified

## Acknowledgements

- 	R. Alforque, A. Blednykh, A. Broadbent, P. Cameron, B. Dalesio, L. Doom, R. Heese, G. Ganetis, D. Hseuh, E. Johnson, S. Kramer, F. Lincoln, R. Meier, I. Pinayev, J. Rose. S. Ozaki, S. Krinsky, B. Mullany, V. Ravindranath, S. Sharma, J. Skaritika, T. Tanabe, T. Shaftan, W. Wildes, F. Willeke, L.Y. Yu.

## Backup Slides

## Diagnostics System Hardware Layout 

- Dipole (BM-A)

- QL1

- QL2

- QL3

- SL3

- SL2

- e-

- Dipole (BM-B)

- Short straight section – 11-ID

- DCCT  Stripline           SCW

- e-

- ~1 m

- 4 diagnostics hardware
- slots at 3 PW locations
- Cell # 26-29

## courtesy Alexei Blednykh

## courtesy Alexei Blednykh

## Loss factor and Power Loss

|  | Ploss, W |  |
| --- | --- | --- |
|  | th=2mm | th=5mm |
| loss, V/pC
s=4.5mm | 3.4 (h=1000)
6.8 (h=500) | 1.6 (h=1000)
3.3 (h=500) |
| loss, V/pC
s=6.5mm | 1 (h=1000)
2 (h=500) | 0.5 (h=1000)
0.9 (h=500) |
| loss, V/pC
s=30mm | 0.03 (h=1000)
0.07 (h=500) | 0.01 (h=1000)
0.03 (h=500) |

|  | loss, V/pC |  |
| --- | --- | --- |
|  | th=2mm | th=5mm |
| s=4.5mm | 5.2e-3 | 2.5e-3 |
| s=6.5mm | 1.5e-3 | 0.7e-3 |
| s=30mm | 0.05e-3 | 0.02e-3 |

- Iav=500mA, T0=2.6e-6m

**Loss factor and Power Loss**

## Partial Compilation of Relevant Parameters