Commissioning of theBeam Conditions Monitor of the

LHCb Experiment at CERN

Ch. Ilgner, October 23, 2008on behalf of the LHCb BCM group at TU Dortmund:

M. Domke, S. Köstner (CERN), M. Lieng, M. Nedos, J. Sauerbrey, S. Schleich, B. Spaan, K. Warda

Beam conditions monitoring• motivation: protecting sensitive detectors

in HEP experiments• readout concept and integration into LHCb

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

The LHCb BCM project at TU Dortmund is supported by:

Implementation in LHCb

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

Sensitive devices, such as the

Vertex Locator („VeLo“), need

protection from adverse beam

conditions.

The VeLo, Courtesy of LHCb VeLo group

-2131mm +2765mm

BCM-U BCM-D

Accident Scenarios – Time Scales

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

Name Operation mode Loss type Loss location ΔT/turns

D1 warm collision local triplet/collimator 5

damper injection local arc/triplet 6

warm quadrupoles

any distributed collimator 18

dump septum any local diluter kicker/septum 35

warm orbit corrector

aollision local triplet/collimator 55

RF (?) any local arc/triplet/septum 55

D1 warm injection local arg/triplet/collimators 120

D1 Cold collision local triplet/collimator 220

warm orbit corrector

injection local arc/triplet/collimator 250

MB quench collision local triplet/collimator 280

after V. Kain, R. Schmidt, R. Assmann, EPAC 2002

D1 magnet failure:

fastest generic beam-loss scenario, timescale: 5 turns ~ 500 μs

→ defines the response time scale (beam dump becomes effective after 270 μs (max., depending on the position of the abort gap)

(anything faster than that could help in LHC commissioning)

Radiation Levels in the Vertex Locator and the BCM

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

X-check:

VeLo signalBCM-D signal

What VeLo sees (in last Si plane) if it gets hit by one 7 TeV proton:

What BCM-D sees (energy deposition (sum over all 8 diamond sensors) if VeLo gets hit by one 7 TeV proton:

Simulated Energy Deposition in the Vertex Locator

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

Normal LHC runningconditions over 107s(15MHz event rate):

• 13.3 kGy for „upstream“ BCM sensors

• 3.4 kGy for„downstream“ BCM Sensors

• 10.6 kGy for VeLoSi paddles

(Simulations: M. Lieng)

Failure scenario: MCBX.1L8 magnet with reversed field at full strength.BCM-D signals as multiples of nominal signal

Energy deposition of 40μs of minimum-bias eventsin the Vertex Locator (VeLo):

Energy deposition of 40μs of minimum-biasevents in the Vertex Locator (VeLo):

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

BCM-D Station tested at ELBE Facility (FZD)

Exposure to 71fA to 225pA electron beam current (20MeV) in order to calibrate diamond sensors and analogue frontend electronics.

Beam currents through sensors: 5.62 pA, 39.6 pA, 805 pA, 2.59 nA, 17.8 nA.

Sensor currents: 1nA-3 μA.

The support by FZD staff (P. Michel, U. Lehnert et al.) is greatly appreciated.

LHC-Experiments Data Exchange

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

Courtesy ofR. Jacobsson

General Machine Timing (GMT)

Beam Dump System

VeLo Interlocks

Beam Conditions MonitorLHC Injection

BCM ok

Safe Beam Flags,Post-Mortem Trigger

Injection Inhibit

Beam Dump(BIS) LHCb

ExperimentControlSystem(ECS)

Injection Inhibit, Status & Flags

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

Beam-Abort Logics

12

32 (1280 μs)

FPGA features three parallel algorithms to trigger an LHC beam dump

Sampling period: 40 μs

Fast abort:80 μs

3 adjacent sensors

consecutively over threshold

Slow abort: 1280 μs

discarding min. and 2 max.

values, summing over

the other values

Single bunch mode:

80 μs3 adjacent

sensors in one CFC frame

OR

Beam abort(effective after <270ms)

Only duringinjection

Coincidence conditions provide protection againsterratic dark currents (commonly known for pCVD diamond detectors)

First LHC beams as seen by the BCM

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

22.08.2008, 20:36h:Max(BCM-D): 500nA (20% of threshold)Max(BCM-U): 50nA(0.5% of threshold)

0 1 2 3 4 5 6 7

0

1000

2000

3000

4000

5000

6000

7000

8000

11:2412:11

12:47

Threshold excesses during exposure of TDI at small particle fluxes:

threshold

Dump logics have been successfully tested.

Conclustion

Ch. Ilgner (TU Dortmund), NSS-MIC 2008, Oct. 23, 2008

LHCb BCM measures ...... CCC operator confirms three

turns.

The LHCb Beam Conditions Monitor has been successfully calibrated, integrated into the LHCb control structure and proven to monitor reliably the particle flux at startup of CERN‘s Large Hadron Collider. A careful but realistic test has shown that the dump logics work reliably.