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

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

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

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

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

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

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

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

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

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

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

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