Location and Specifications for BLMs in the PSB Injection Region

Present: R. Versaci, Ch. Zamantzas, B. Dehning, U. Raich, B. Goddard, Ch. Carli, A. Lombardi, K. Hanke and B. Mikulec

1. Introduction

Whereas the location of the BLMs in Linac4 and the transfer line is relatively well defined, the requirements of the PSB injection region have not yet been finalised. The aim of this meeting was to define at least the location of all BLMs to be able to estimate cabling requests (deadline end of this month).

2. Location of BLMs

B. Goddard summarized the needs concerning beam loss measurements in the PSB injection region in his presentation. In particular the region of the injection bump (BS magnets) is critical containing the injection foil and the H0/H- dump behind. Injection losses have to be kept well under control. In addition space is very restricted there.

The following tables show a summary of the requested location of all BLMs in the Linac4 transfer and measurement lines (13 BLMs), the PSB injection region (17 BLMs), the PSB ring and the PSB transfer lines (52 BLMs). The location of the Linac4 BLMs has already been defined elsewhere.

PSB BLMs to be renovated:

It has been stressed that the cable length should include some margin to displace the BLMs to positions that might turn out to be more adequate. Please keep in mind that the debuncher position will most probably change compared to the original drawings; currently it is proposed to move it downstream by approximately 13 meters (to be confirmed).

Previous FLUKA simulations of R. Versaci (see https://twiki.cern.ch/twiki/bin/view/SPL/Minutes14December2009 and the presentation) show that the signal for losses in one ring decreases considerably between the concerned ring center and the mid-point of 2 adjacent rings; therefore the 4 BLMs in the injection region should be placed at the level of each ring center. It has to be checked if enough space is available (most probably align the BLMs 90 deg. wrt. to the beam.

3. BLM specifications for PSB injection region

• max. loss: 2.5 E13 protons/ring (x4 for BLMs in common BI line)
• min. loss: 1 E08 protons/ring
• time resolution: 2 us has been accepted (as proposed for Linac4)
• synchronised with PSB injection: have at disposal the first 500 samples after injection with 2 us resolution (corresponds roughly to the first 1000 turns); in addition take 1 ms samples during the time when beam is in the PSB (during 530 ms). Currently the PSB BLMs have 1 ms sampling accessible by the operators via the samplers. This functionality should be kept.
• The BLMs have to be ppm (knowledge of the current user in the cycle; plan for 32 users). User-specific settings: threshold and disabling/enabling of BLM. This is also valid for the Linac4 BLMs!

4. Connection to the beam interlock system (BIS)

There is only one entry reserved in the BIC modules per interlock zone (see tables above for the definition of the interlock zone). An implementation has to be foreseen at the hardware level to increment bad shots per user up to a predefined number and decrement this running value in case of good shots. A logic 'OR' of the status of all BLMs of one interlock zone will yield the input for the BIC module of this zone and will stop the beam for that specific user in case one of these BLMs exceeds the predefined number of bad shots.

Only the 4 BLMs installed after BS4 should stop the beam immediately if over threshold, as they should indicate a foil failure. One more BIC input channel is reserved for the logic 'OR' of these 4 BLMs.

Currently, no need has been expressed for the installation of fast BLMs that would react within few hundreds of ns. In any case, these fast BLMs would only be connected to OASIS and not to the interlock system.

-- BettinaMikulec - 25-Jun-2010

• PSB_injection_BI_BLM.pdf: Specifications for BLMs in PSB injection region.