Speaker
Description
Summary
The beam loss monitoring system for the LHC uses a radiation tolerant acquisition
card (BLECF) to measure the current of ionization chambers. The data are transmitted
to the surface to a VME board (DAB) using optical links. The data are processed in
it and decisions are taken in case of dangerous losses. In order to visualize and
test the BLECF in an efficient way, a single board with dedicated software has been
developed with flexible and powerful features.
The board is able to check the linearity of the measurement from the BLM acquisition
card. A complex current source has been developed to be able to feed the inputs with
current from 10pA to 1mA (8 orders) with a reasonable accuracy (better than the
input tolerance). To check if the results are in the expected tolerances a sequence
of current settings is launched with the software to scan the whole dynamic range.
When the system works in the similar mode to the future LHC system (Running Sums
acquisition), it is possible to check different indicators like the number of wrong
Cyclic Redundancy Check (CRC) of the optical link or the type of error appearing in
the receptions of the packet. In order to check specific data during the development
of the BLECF, visual displays have been implemented in the software for the values
of the current-to-frequency converter and the sampled value of the Analog to Digital
Converter (ADC) entering in the calculation of the final current.
The use of a USB module has been launch by a student in his thesis. The choice of
the modules have been determined by their speed which they reached (use of USB 2.0)
and by the availability of a complete library of functions. The optical receivers
use photodiode with automatic gain control and are interfaced with an 8b/10b
transceiver. The FPGA holds the reception logic for the data, the processing of them
(taken from the future LHC BLM system) and the logic for the link to the PC
(including control and acquisition). The software is able to integrally control the
board in its different mode of operation including a reading of the raw data, a high
speed reading, visualization of the resulting processing of the FPGA calculation
(running sums) and the functional and linearity tests. The program has been written
in C and linked with a user friendly interface. The board can be powered over the
USB of a laptop.
The system has been successfully used during the development phase at CERN and
especially used by the designer of the BLECF during the validation of the FPGA
description. Since the processing of the data is similar to the final system and
very compact, the board has been successfully used as readout system during
radiation tolerance campaigns for the BLECF at PSI. For the same reason, the system
will also be used during installation and commissioning of the LHC BLM. Another use
of this system will be the investigations for the beam condition monitor of the LHC
CMS experiment using diamond detectors.
