NSLS-II Accelerator System Advisory Committee Review

1
NSLS-II Accelerator System Advisory Committee
Review Diagnostics Design and RD Om Singh
Group Leader July 17-18, 2008
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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
• 
  

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SR Cell Diagnostics Systems BPM Beam Loss
Monitors
C) X-ray BPMs up to 2 / FE
D) Slow Fast Correctors
3PW or BM B-Line
ID Beamline
SC FC
FC FC
FC SC
BPM
BPM
BPM
BPM
BPM
BPM
BPM
BPM
B) Small Gap RF BPMs ? 2 or 3 per Cell Button
Assembly on a Stand or ID Chamber
A) Standard Gap RF BPM ? 6 per cell
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
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SR Diagnostics Hardware Locations - Preliminary

Odd Cells Even
Cells
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NSLS-II Lattice Functions Electron Beam sizes /
divergences
Lattice Functions
Electron Beam Sizes Divergences
Most challenging Beam stability Requirements
0.31 µm
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NSLS-II SR RF BPM System Performance
Requirements
Requirement values are preliminary - work in
progress ID BPM system resolution values will
be smaller ( factor of 0.5) _at_ 5 mA 50 mA
stored beam, BPM receiver resolution values will
be worse (factor of 2)
(Req. met - Test Data Later)
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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 _at_ 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)
SY0.04
SX0.12
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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

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BPM Evaluation - Proposed Design (cntd)

• Proposed Design (two button/flange)
• Matlab Simulation shows
• ? input power level _at_ 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
Resolution
SY0.09
SX0.09
-8 dBm
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Flange Layout 7mm buttons
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RF BPM Button

• Button Heating

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

• 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).

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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 _at_ ESRF
• in the range of 100oC _at_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

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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 _at_ 2 mm 0.007 V/pc _at_ 5mm
• Repeat the analysis with Microwave Studio
  simulation
• Ongoing communication/collaboration with other
  labs

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ID BPM Button - Baseline Design
Established Design used at APS Elettra
Flanges mounted on top bottom of Small gap
Chamber
Two 4 mm Dia buttons HS 10 mm

• Baseline design provides adequate sensitivity
  SX0.26 SY0.14
• 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.

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Sensitivity Optimization Rotated Flange
Sensitivity vs H-separation

• 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
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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

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ID-BPM Stable Support

Specification ? Total Thermal expansion lt 100 nm
R. Alforque

• 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

10 Dia Carbon fiber composite stand limits
thermal expansion to 20 nm/m/0.1oC
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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 (t 1 week)
• Thermally isolate the test post, use heaters to
  vary temperature (t 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

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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

at both ends measure relative displacement due
to temperature variation
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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

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Stand for Stability Test for Libera Brilliance

• 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

External Clock
Reference 10 MHz
Repeater
system clock
Libera Brilliance
Gated Oscillator
Func. Generator
machine clock
A
B
C
D
4-way Splitter
Attenuator
500 MHz
Attenuator
Attenuator
Attenuator
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First Results from the Libera Tests Meet Drift
Spec.
TEMP 1 oC
TEMP
HOR 200 nm
HOR
7 Hrs
VERT 100 nm
VERT

• 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

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Pinhole Camera with 3PW Source
3PW has higher magnetic field (1.14 T) than
dipole. Shorter critical wavelength provides
better spatial resolution. Large vertical
ß-function (21 m) gives large beam size (12.4 µ).
Horizontal beam size is defined predominantly by
energy spread (sE/E?170µ) rather than emittance
(1nm4.1m)½64µ. 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)

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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

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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

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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.

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Backup Slides
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Diagnostics System Hardware Layout
Short straight section 11-ID
e-
1 m
DCCT Stripline SCW
Dipole (BM-A)
QL3
SL3
QL2
SL2
QL1
Dipole (BM-B)
e-
4 diagnostics hardware slots at 3 PW
locations Cell 26-29
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courtesy Alexei Blednykh
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courtesy Alexei Blednykh
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Loss factor and Power Loss
Iav500mA, T02.6e-6m
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Partial Compilation of Relevant Parameters