Hi Lum ATLAS Endcap Project Collaboration of Arizona
Hi. Lum ATLAS Endcap Project § Collaboration of Arizona, Dresden, JINR Dubna, Kosice, Mainz, LPI Moscow, MPI Munich, BINP Novosibirsk, IHEP Protvino, TRIUMF, Wuppertal. § Goal: establish limitations on the operation of the endcap calorimeters (FCAL, EMEC, HEC) at highest LHC luminosities. § INTAS Project 05 -103 -7555 § R&D: 'mini modules‘ of FCAL, EMEC and HEC type, each in one separate cryostat; § IHEP Protvino: beam line # 23: extraction via channeling in bent crystal gives widest available rate variation from 10**7 up to 10**12 p/spill; E= 50 Ge. V; RMS width up to 35 mm (need to have as homogeneous coverage as possible of front face of module!); P. Schacht Hi. Lum Protvino project - status February 2009 1
Ion Build-up r=1 § Potential V § Dc is critical ionization rate where charge buildup in gap is equal to charge on electrodes § D is actual ionization rate § r=D/Dc J. Rutherfoord, NIM A 482 (2002) 156 P. Schacht Hi. Lum Protvino project - status February 2009 2
Ion build up: where are we now? Limit r=1 s. LHC § § § P. Schacht Hi. Lum Protvino project - status February 2009 EMEC and HEC OK FCAL: reduce gap from 250 to 100 ! all endcap calorimeters stay in region r 1! 3
LAr Signal: study rate dependence of response Signal samples § Bunch: width 30 ns at 5%, about 15 ns FWHM; bunch spacing Δt=166 ns § Run machine in ‘debunching off mode' § Spill: ´ 1 -2 s, spill cycle time: 10 s § Use random trigger on bunch, read-out up to 252 time slices separated by 25 ns • IHEP runs with only 5 bunches per turn (out of 30), i. e. almost 1 s between single bunches! • i. e. reconstructed signal depends only on intensity in present bunch, except for ion build-up effects (which we want study!!!!) P. Schacht Hi. Lum Protvino project - status February 2009 4
Cryostats in the IHEP Beamline: η dependence of energy deposited as close as possible to ATLAS P. Schacht Hi. Lum Protvino project - status February 2009 5
Beam intensity related parameters § FCAL § EMEC § HEC P. Schacht Hi. Lum Protvino project - status February 2009 107 108 109 1010 1011 1012 6 pps
Beam intensity monitoring (spill) § Low intensity (up to 107 pps): scintillation counters S 1, S 2, S 3 in beam, at somewhat higher intensities: S 4, S 5, S 6 at 45 § Intensity 107 -1010 pps: low pressure ionization chamber; cross calibrate at low intensity with scintillation counters; § High intensities (5 1010 – 1013 pps): secondary emission chamber (metal foils in vacuum, 70 mm diameter, 16 horizontal and vertical signal Al strips on polyimide foils); cross calibrate with Al activation (foil, 27 Al(p, 3 p 3 n)22 Na, 22 Na→γ(1275 ke. V), σ=10. 6 mb) P. Schacht Hi. Lum Protvino project - status February 2009 7
Beam intensity monitoring (bunch) § Cherenkov, air, vary pressure and HV of PMT; § 12 bit ADC with 32 Mb memory, up to 106 bunch intensities per second; data transferred to normal data stream in between spills; § In addition, data for triggered event (random trigger, at least 72 time slices, i. e. at least 2 filled bunches) are fed via calorimeter readout to normal calo ADC; in this case the full history of previous bunches is of course not available; P. Schacht Hi. Lum Protvino project - status February 2009 8
Beam intensity monitoring (bunch) § Cherenkov efficiency: fit yields average number of photoelectrons for a given HV; § Cherenkov spectra calibrate the single phoelectron peak; P. Schacht Hi. Lum Protvino project - status February 2009 9
Cryogenic system § Three independent cryostats § Electronics for regulation outside of radiation region § LAr purification system § 2 oxygen meters P. Schacht Hi. Lum Protvino project - status February 2009 10
Hi. Lum FCAL module 90 mm 60 mm 50 mm deep 4 readout channels per side 8 readout channels in all P. Schacht Hi. Lum Protvino project - status February 2009 11
Hi. Lum FCAL module: front view 2 nd Cooling loop! • LHC module with 250 gap • s. LHC module with 100 gap Size of modules should match (approximately) beam size ! Tube Group P. Schacht Hi. Lum Protvino project - status February 2009 12
Hi. Lum FCAL module P. Schacht Hi. Lum Protvino project - status February 2009 13
HEC module § 4 'standard' HEC gaps (HEC 1) § 4 read-out channels § 4 HV lines (one per subgap) P. Schacht Hi. Lum Protvino project - status February 2009 14
EMEC module § 4 Pb absorber plates (70 x 70 mm) § 3 electrodes § 4 pads for read-out P. Schacht Hi. Lum Protvino project - status February 2009 15
Liquid argon purity monitoring P. Schacht Hi. Lum Protvino project - status February 2009 16
Liquid argon temperature monitoring § Rise of FCAL temperature when switching from low to high intensity P. Schacht Hi. Lum Protvino project - status February 2009 17
Read out chain § FEB-1 board (HEC testbeam) § HEC testbeam 40 MHz ADC‘s; § Second ADC had clock shifted by 12. 5 ns § ‚effective‘ sampling rate 12. 5 ns; P. Schacht Figure 9: Schematic diagram of the electronics chain. Schematic diagram of electronics chain Hi. Lum Protvino project - status February 2009 18
Noise and calibration pulse shape Noise P. Schacht time, ns Figure 10: Measured (points)and modelled (line) calibration Measured (points) modeled (line) pulse response. calibration pulse response Hi. Lum Protvino project - status February 2009 19
Signal response for different ionization rates P. Schacht Hi. Lum Protvino project - status February 2009 20
HEC response (sum of 4 channels, normalized) § e. g. HEC signal reconstruction: ranging from 2*107 pps up to 1. 8 *1011 pps (amplitude is normalized!) § At higher intensities bunch to bunch variation of intensity! P. Schacht r=1 Hi. Lum Protvino project - status February 2009 r=11 21
Hi. Lum Experiment § Mean signal of the 4 HEC channels as function of spill averaged intensity (caveat: will change! Now we have bunch intensity measurement!!) P. Schacht Hi. Lum Protvino project - status February 2009 22
FCAL: variation with bunch intensity § Low intensity: signal proportional to intensity § Higher intensity: signal proportional to (intensity)3/4 – as expected § Very high intensity: yet to be understood P. Schacht Hi. Lum Protvino project - status February 2009 23
FCAL: HV current measurements § Four 24 bit ADC’s § Resolution ~ 20 n. A § Ten measurements per second per channel § Data integrated over spill § Comparison to beam intensity as measured with ionization chamber P. Schacht Hi. Lum Protvino project - status February 2009 24
FCAL (250 μm): HV current measurements § Fit: nonlinearity less than 0. 36% (95% CL) at 109 pps; § 109 pps corresponds to 1034 at LHC; OK for Lumi measurement at ATLAS! P. Schacht Hi. Lum Protvino project - status February 2009 25
Hi. Lum Run status § Three technical runs: 1 -7 October 2007, 3 -10 November 2007, 2 -9 April 2008; § Three beam runs so far: 10 -18 November 2007, 9 -14 April 2008, 9 -19 November 2008; § Two more runs planned: April 2009 (? ), November 2009 § Status: – Analysis ongoing – but not enough manpower! – All major components well under control! § More final results expected soon …. P. Schacht Hi. Lum Protvino project - status February 2009 26
- Slides: 26