1. Luminometer Integration at IR2
3 October 2003
Enrico Bravin AB-BDI
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

2. LHC LUMINOSITY (RATE) MONITORS
LBNL is responsible for the design and production of the TAS and TAN absorbers for IP1 and IP5.
Bill Turner of LBNL has proposed to put some kind of instrumentation in these absorbers in order to measure the luminosity (or better the relative interaction rate.)
After a number of iterations the decision was to instrument only the TAN's in IP1 and IP5, but also to install the same kind of monitors in IP2 and IP8.
Two kind of technologies are under study for the detectors
Ionization Chamber (most probable choice)
CdTe solid state detectors
In IP2 and IP8 there are no TAN's and an absorber must be put in front of the detectors in order to generate the showers (3cm of Cu for CdTe and 30cm of Cu for the IC)
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

3. Monitors specifications
A specification document has been prepared for the luminosity monitors of LHC
“Measurement of the relative luminosity at the LHC”
LHC-B-ES-0007
R. Assmann, J.P. Koutchouk, M. Placidi, E. Tsesmelis
... Standardized, simple, fast and robust machine luminometers are provided to set up the machine for physics, optimize its performance and compare it from run to run. The luminosity may be calibrated by comparing with the luminosity from the experiments and by the van der Meer method (cross-check of instruments, e.g. profile monitors). From experience, cross-checks with data from LHC detectors are equally valuable to understand possible differences in the luminosities of LHC IR’s. ...
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

4. Luminosity modes at IR2 Bunch population Number of bunches
Bunch spacing
Mode
IP beta
Luminosity [cm-2 s-1]
Collision studies with single pilot bunch, no crossing angle
5x109 1
p-p
10 m
3.61026
Collision studies with single high intensity bunch
1.11011
1.81029
Nominal p-p luminosity run
2808
25 ns
1.01030
Ion runs
7107
Pb-Pb
0.5 m
0.91024
592
0.51027
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

5. Machine conditions AT IR2
IP beta
Crossing angle plane
Half total crossing angle
Range for nominal cases
10 m
Vertical
±150 mrad
±(35-150) mrad
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

6. Luminometer Integration at IR2 E. Bravin AB-BDI
Anticipated Use
Initial beam finding &overlap maximization
Manual Luminosity Maximization for physics runs
Automated beam overlap feedback
Equalization of the luminosity amongst the experiments
Adjustment of the luminosity for ALICE (p-p)
Minimization of beam excitation
Monitoring of the crossing angle
Bunch by bunch measurement of the luminosity
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

7. Luminometer Integration at IR2 E. Bravin AB-BDI
Accuarcies and rates
Luminosity sub-range
particle
Resolution
integration
time
Beam structure
Luminosity
1.0  1026 1.0  1028
p-p
beam
 10%
~ 1 mn
1.0  1028 3.0  1034
 1% (0.25%)
~ 1 s
1.0  1033 3.0  1034
bunch
~  1%
~ 10s
1.0  1024 5.0  1025
Pb-Pb
5.0  1025 0.5  1027
bunch ?
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

8. Sensitivity to vertex parameters
The relative calibration deals with possible variations of the proportionality factor between monitor signal and actual luminosity. This variation should be less than or equal to the resolution requested for the range of vertex parameters. For a constant crossing angle between the two beams, the trajectory of each beam may change due to machine tuning. We require the luminometer not to be sensitive to such changes within 15 mrad of the average beam direction for constant crossing angle.
Transverse tolerance (x,y)
 3 mm
Longitudinal tolerance (s)
 10 cm (  20 cm to 1m?)
Tolerance on half-crossing direction
  15 rad
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

9. Luminometer Integration at IR2 E. Bravin AB-BDI
Data transfer rates
Data transfer
Rate
Luminosity for optimization (initial running and later)
1 Hz
Luminosity for optimization (low beam intensity)
1/mn
Background for optimization
1Hz
Maximum logging rate of luminosity and background
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

10. Possible technologies
Two technologies are under investigation at the moment. A major constraint on the choice is given by the required radiation hardness necessary to survive in IR1 and IR5
Fast Ionization Chamber (rad hard)
Polychristalline Cadmium Telluride detectors (rad hard but not enough)
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

11. Luminometer Integration at IR2 E. Bravin AB-BDI
Ionization Chamber
The ionization chamber requires ~30cm of Cu in front of it to act as a converter and start the shower
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI

12. Luminometer Integration at IR2 E. Bravin AB-BDI
The CdTe detector
Due to the better sensitivity the CdTe detector does not need to sit at the shower maximum, a few cm of copper would be sufficient.
36.5
3 Oct 2003
Luminometer Integration at IR2 E. Bravin AB-BDI