1. Report on Beam Loss Monitors
Specification
Type of detectors
Location of detectors
Status of developments, production and tests
LEADE, Bernd Dehning

2. Loss Levels and Required Accuracy
Relative loss levels
450 GeV
7 TeV
Damage to components
320/5
1000/25
Quench level 1
Beam dump threshold for quench prevention
0.3
0.3/0.4
Warning
0.1
0.1/0.25
Absolute precision (calibration)
< factor 2
initial
< factor 5)
Relative precision for quench prevention
< 25%
Functional specification:
LEADE, Bernd Dehning

3. Reliability and Time Resolution
Type
Area of use
Criticality
Time resolution
BLMC
Collimation sections
yes
1 turn
BLMS
Critical aperture limits or critical positions
1 turn (89 us)
BLMA
All along the rings (ARC, …) no
2.5 ms (7.4.4)
BLMB
Primary collimators
bunch-by-bunch
Definition (specs): By criticality, we mean that the system must be 100% operational to allow beam injection and that the beam is dumped if it fails.
In case of a non working monitor this monitor has to be repaired before the next injection
LEADE, Bernd Dehning

4. Quench and Damage Levels
Detection of shower particles outside the cryostat or near the collimators to determine the coil temperature increase due to particle losses
Special &
Collimator
Arc
Damage levels
Quench level and observation range
450 GeV
7 TeV
Bending magnet
Dynamic
108
LEADE, Bernd Dehning

5. Loss Detectors Ionisation chamber few litre volume Secondary emission
diameter = 8.9 cm, length 15 cm
Secondary emission
monitor
diameter = 8.9 cm, length 60 cm, 1.5 litre
LEADE, Bernd Dehning

6. Location of Detectors (I)
Distinguish between beams
Observe losses due to magnet misalignments
Observe losses due to orbit changes and emittance growth
Exact longitudinal position not defined yet
Impact of protons in the centre of the quad. magnet
LEADE, Bernd Dehning

7. Location of Detectors (I) (One side of IP only, has to be multiplied by two to get the number per IP, if not indicated differently. Only one beam, if not indicated differently)
LEADE, Bernd Dehning

8. Status of BLM’s Ionisation chamber and SEM:
BIC (Dump)
Ionization
Current to
Multi-
Diode
Threshold
Beam Permit
Chamber or SEM
frequency
plexer
Demulti-
comparator
Beam Energy
converter
LASER
plexer
VME Bus
Below Quad. in ARC
At surface (SR, SX)
Analogue Electronics
Digital Electronics
Ionisation chamber and SEM:
final tests with proto
production contracts in preparation
Installation start in 09/2005
Current to frequency converter:
Prototype tests in SPS ( - 11/2004)
Radiation tests at PSI (06/2004)
Transmission link (optical):
GOL/GOH from CMS
DIODE/TLK proto in 11/2004
Threshold comparator
DAB TRIUMF BPM/BLM
Proto 08/2004
Complete Proto system 12/2004
This is the general layout of the BLMS. We have 3200 IC of almost 70 plates 50 cm long placed all around the quadrupoles, 6 per magnets, that generates a current that is sent to the front end electronics.
This analog electronics converts current, of range 1 pA -1ma, into frequency, essentially with an integrator, a threshold comparator, a monostable and a switch. The digitize signal is counted and multiplexed by an FPGA in the tunnel, transmitted trough two optical lines to the surface where is de-multiplexed and analysed by another FPGA( actually, our FPGA are Stratix but not the GX version). This FPGA compares the measured values with the threshold table and, in case of need, inhibits the dump permit through the BIC. It has to be noted that the levels are time dependent (from 100 micros to 100 ms) and energy dependent. Just a remark: the total range to cover is around 9 decades.
How we can improve the system reliability?
LEADE, Bernd Dehning

9. Notation: (BLMS: Monitors in the Straight Sections, Triplett, D1, D2)
Functional specification
Engineering specification
time
remarks
BLMA
BLMAI
2.5x10-3 to 100s
Monitors at all quadrupole magnets, ARC (except if other specified)
BLMB
Every bunch
Monitors with single bunch resolution
BLMC
BLMCI + BLMCS (CI+CS)
1x10-4 to 100s
Monitors in the collimation area (I: ionisation chambers, S: secondary emission monitors)
BLMS
BLMSI (SI)
Special location ionisation chamber (low region of dynamic range)
BLMS*
BLMSS (SS)
Special location secondary emission monitors (high region of dynamic range)
LEADE, Bernd Dehning