1. Use of Beam Loss Monitor type detectors in CNGS muon station
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

2. Valeri Falaleev & Gianfranco Ferioli
Talk overview
1. Muon monitoring at CNGS
2. Beam Loss Monitor (BLM) as muon detector
at CNGS
3. Summary
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

3. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS
Main beam parameters
Proton
beam
Target
Horn
He tube
Reflector
2.7
43.4m
100m
Decay pipe
Hadron stop
 detectors
1092m Fe C
18m
67m
SEM foils 5m 
Burst duration s
Time between 50 ms / 6 s
bursts 2
 Muon fluxes x104 – 4.5x107 p/cm2
x-slice (m)
 / 1013pot / cm2
x107
x105
A system based on a set of fixed
and movable SSD’s
(like at WANF).
Original proposal
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

4. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS (2)
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

5. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS (3)
CNGS features and special requirements
• No access to the muon chambers during the runs,
minimal number of accesses during the shutdowns
=> detectors should be very reliable
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

6. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS (4)
> 500 m
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

7. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS (5)
CNGS features and special requirements
• No access to the muon chambers during the runs,
minimal number of accesses during the shutdowns
=> detectors should be very reliable
• The detectors and electronics are separated by the distance of more then 500 m.
=> detectors signal should be high
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

8. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS (6)
 CC events normalized (%)
First muon chamber X (cm)
Horn lateral displacement
3 mm
99.0
10.1
-0.6
6 mm
97.2
19.1
-3.5
Reflector lateral displacement
10 mm
99.6
5.7
-10.7
20 mm
98.4
14.7
-12.6
Proton beam lateral displacement
0.5 mm
100.3
7.3
1.0 mm
-1.2
14.8
Proton beam angular displacement
0.5 mrad
100.0
3.7
1.0 mrad
98.7
2.3
10.4
stat
0.2
0.5
1.2
 / 1013pot / cm2
 / 1013pot / cm2
Aligned case
Mis-aligned case
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

9. Valeri Falaleev & Gianfranco Ferioli
Muon monitoring at CNGS (7)
CNGS features and special requirements
• No access to the muon chambers during the runs,
minimal number of accesses during the shutdowns
=> detectors should be very reliable
• The detectors and electronics are separated by the distance of more then 500 m.
=> detectors signal should be high
• No significant changes in the  event rate at Gran Sasso even for important
misalignment of beam elements or mis-steering of the beam.
=> detectors resolution can be moderate
• Flux variation is smooth. No need for absolute flux measurement.
=> detectors can be big in transversal direction
• Cost limitation.
=> detectors should be as cheep as possible
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

10. Valeri Falaleev & Gianfranco Ferioli
BLM as muon detector (1)
General parameters
• sealed ionisation chamber.
• widely used at CERN last 30 years.
• there are about 300 BLMs around the SPS and about 3000
new BLMs will be fabricated for LHC 
92
5 6
Filled with 99.9% N2 at about 1.1 bar
Active volume is 1250 cm2
Bias voltage 800 – 1200 V
Signal electrodes
Construction
All isolation is
done from ceramic
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

11. Valeri Falaleev & Gianfranco Ferioli
BLM as muon detector (2) 
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

12. Valeri Falaleev & Gianfranco Ferioli
BLM as muon detector (3)
HV and electronics
1M
+ 1000V
2.2 F
• collected charge is 10 times more then for SSD
• 18 channels (twisted pairs) signal cable up to 1500m length
• read-out is sincronized with 50 Hz
• common HV powers supply for all chambers
• well developed shielding scheme
• a few % long term stability calibration with 127Cs (3 mCi) source
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

13. Valeri Falaleev & Gianfranco Ferioli
BLM as muon detector (3)
Preliminary linearity test
2.5 s slow extraction
flux from 102 to 105 p/cm2
50/50 mixture of 120 Gev protons
and pions
Target
Proton
beam
Proportional Ionisation
Chamber
(PIC)
Scintillator + PM
BLM
Collimator
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

14. Valeri Falaleev & Gianfranco Ferioli
BLM as muon detector (4)
Week points of BLM
• linearity at highest intensity (4.5x107 p/cm2 for nominal CNGS beam)
- space charge limit at 4 x 107 p/cm2 (6mm gap, 1kV)
- not optimized detector construction
Possible solutions: better design of new LHC BLM,
calibration with reference chamber
• a bit much of material: difficulties for calibration and beam scan
Possible solutions: better design of new LHC BLM
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli

15. Valeri Falaleev & Gianfranco Ferioli
Summary
The Beam Loss Monitor is a suitable device for
CNGS muon monitoring station and can be used
as both fix and movable detector.
Further design work on new BLM and study of
chamber characteristics are needed.
3th workshop on NBI, March 2002
Valeri Falaleev & Gianfranco Ferioli