STORAGE RING
Next figure shows the mechanical design of the button feedthroughs and blocks of the 120 Storage Ring BPMs
Design of the vacuum chamber was set by the Vacuum Group, and only the distance between buttons in the BPM block
was defined by us (buttons center separation).
Buttons position and electrode design was analyzed with a Matlab GUI and crosschecked with SuperFish calculations.
Final decided parameters were:
| Parameter | value |
|---|---|
| buttons centers separation (bcs) | 18.1 mm |
| electrode diameter (d) | 7 mm |
| electrode thickness (t) | 4 mm |
| electrode-shell gap (g) | 0.3 mm |
With these parameters, the expected performance of the SR buttons is summarized in the following table (power calculations done by T. Günzel):
| Parameter | value |
|---|---|
| button capacitance (Cb) | 2.7 pF |
| horizontal sensitivity (Sx) | 0.080 mm-1 |
| vertical sensitivity (Sy) | 0.075 mm-1 |
| intrinsic resolution @ 1.115 MHz - 0.1 mA | 186.6 um |
| intrinsic resolution @ 1.115 MHz - 1 mA | 18.66 um |
| intrinsic resolution @ 10 kHz - 1 mA | 1.77 um |
| intrinsic resolution @ 10 kHz - 50 mA | 35 nm |
| intrinsic resolution @ 10 kHz - 100 mA | 17 nm |
| intrinsic resolution @ 10 kHz - 400 mA | 4 nm |
| power losses per button (MultiBunch) | 0.19 W |
The measured electrical offset and the corresponding eBPM electronics settings can be found
here.
BPMs position in the Storage Ring
Following figure shows the placement of the BPM blocks (brown), and their corresponding correctors (green), in one quarter of the Storage Ring.
Out of the 120 installed BPMs, only 88 will be used in the beam position correction scheme (see ALBA fofb - draft, M. Muñoz and Initial Design of a Global Fast Orbit Feedback System for the ALBA Synchrotron
, M. Muñoz, D. Beltrán - ICALEPCS'07).
Three extra BPM blocks will be installed in the Diagnostics Sections for Tune Measurement and Multibunch instabilities correction. Following images show their placement in the diagnostics sections (Click to enlarge).
Thermal Analysis
From the power losses previously calculated (0.19 W per button), a thermal analysis of the BPM block was done by L. Nikitina to study the heating up of the electrodes and the possible displacement of the feedthroughs. Following image shows that a maximum temperature of 34ºC will be reached at the electrode level.
Results of the simulations can be found here, and are summarized as:
| Parameter | value |
|---|---|
| max. electrode temperature | 34ºC |
| max. block deformation | 5.7 um |
| max. block stress | 107.6 MPa |
| max. button deformation | 3.48 um |
More information about Storage Ring BPMs:
- BPMs characterization at ALBA, paper BIW10 (A. Olmos, M. Álvarez, F. Pérez)
- BPMs characterization at ALBA, poster BIW10 (A. Olmos, M. Álvarez, F. Pérez)
- Sorting of the remaining batches of SR buttons (A. Olmos)
- Sorting of the first batch of SR buttons (A. Olmos)
- Study of Electron Pickups (A. Olmos)
- Electric Field on the Button Pickups (A. Olmos)
- eBPMs Intrinsic Resolution (A. Olmos)
- Guide for the selection of the button pickups diameter (A. Olmos)
- BPM plugs thermal-structural simulation (L. Nikitina)
- The optimisation of the BPM-buttons (T. Günzel)
- 2nd MAC meeting (A. Olmos)
- 4th MAC meeting (A. Olmos)
- 5th MAC meeting (A. Olmos)
- 2nd Accelerators Division meeting (A. Olmos)
- ALBA eBPMs system, 14th ESLS workshop (A. Olmos)
- BPM Desgin for the ALBA Syncrotron, EPAC06 (A. Olmos, T. Günzel, F. Pérez)
- Beam Orbit Control at ALBA - Seminar 17 Oct 2007 (A. Olmos)
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