BOOSTER and BTS

 

Following the same procedure than for the Storage Ring BPMs, the mechanical design and the obtained characteristics of the 44 Booster blocks and feedthroughs are:

 

 

Electrical Offset calculations

 

All button feedthroughs have been measured during the manufacturing process of the BPM blocks in order to analyze their deviation from specs and to have a feeling of the Electrical Offset on the BPM due to non-equal buttons. These tests also allow us to have a tracking of the BPMs quality during the manufacturing. Keep in mind that the ALBA Booster BPMs are directly welded on the vacuum chamber and any defect on the BPM block means that the complete chamber must be replaced. For that reason, intense checking of the feedthroughs quality on each stage is almost mandatory.

 

Buttons capacitance value was measured using a TDR device:

• After buttons manufacturing
• After buttons welding on the BPM block
• After BPM block bakeout

 

A sorting process of all buttons (230) was done before welding in order to select the more suitable buttons for each BPM. As said, after welding and after baking the buttons were measured again. An Excel

file was created in order to track the capacitance changes during the different stages.

 

Following figure shows the measurement of the capacitance values of the buttons just after reception from the manufacturer (original) and their final values after the bake out process.

 

Mean value has shifted a bit down from 3.23pF to 3.15pF. Next images represent some statistics to compare the results.

 

 

The buttons capacitance deviation from specs remains in all cases below +-10%, with an absolute average value of 3.2%, maximum change on a button of 8% and minimum of -5.3%.

 

All these variations of capacitance during the manufacturing process of the BPMs leads to an Electrical Offset effect on the BPM readings (only due to the buttons difference). It can be calculated using a Matlab based tool.

 

Extra effect will be introduced by the relative positioning of each one of the 4 buttons on a BPM block (to be measured later using a Network Analyzer test).

 

Plotting the calculated electrical offsets of the BPMs (below), we can have a feeling of a "first stage" position offset we'll have on the Booster. Figures show "how good" was the original sorting of buttons, that led to zero electrical offset in both planes and the final effect due to different buttons capacitance.

 

 

The results of these calculation can be found here, as well as a sheet

that relate BPM blocks with buttons, capacitances, offsets and their physical position on the Booster ring (Vacuum chamber type, Quadrant and Unit).

 

Obtained offsets are low, so we believe that they are due to the limited resolution of the TDR device and the different environmental parameters during the measurement runs.

 

More information about Booster 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)
• Electrical offset variation on Booster BPMs (A. Olmos)
• Sorting of the first batch of Booster buttons (A. Olmos)
• Preliminary studies for the ALBA Booster button pickups (A. Olmos)
• 4th MAC meeting (A. Olmos)
• 5th MAC meeting (A. Olmos)
• 14th ESLS workshop (A. Olmos)
• BPM Desgin for the ALBA Syncrotron, EPAC06 (A. Olmos, T. Günzel, F. Pérez)

 

 

TRANSFER LINES

 

BPM blocks and buttons for the Transfer Lines will have:

• same design as the LINAC for the LINAC To Booster (LTB) BPMs --> 3 units (scheme by U. Iriso)
• same design as the Booster for the Booster To Storage Ring (BTS) BPMs --> 4 units (scheme by U. Iriso)