US CMS HCAL Meeting
Boston University
Vasken Hagopian
Florida State University
October 2002
US CMS HCAL at BU
1
HPD QE & K27 Spectrum
HPD Quantum Efficiency
and Spectra
25
RM2
20
RM3
RM4
%
15
RM6
10
RM7
RM8
5
Megatile
0
450
500
550
600
650
Wavelength in nm
October 2002
US CMS HCAL at BU
2
Test Beam results
HPD Variation
1.40
1.30
Ratio of QIE
1.20
Pi-
1.10
e+
1.00
Mu-
0.90
LED
0.80
0.70
0.60
0
2
4
6
8
Phi segment
October 2002
US CMS HCAL at BU
3
QE x K27 Spectrum
RM's in Test Beam
1.40
1.30
1.20
1.10
Ratio
QE x K27 spectrum
100 GeV e-
1.00
225 GeV mu150 GeV pi-
0.90
0.80
0.70
0.60
1
2
3
4
5
6
7
8
9
RM number
October 2002
US CMS HCAL at BU
4
Conclusions
1. The test beam measurements are not
compatible with the QE of the HPD’s.
2. The HPD QE provided by DEP are not
standard bi-alkali nor green extended
bi-alkali.
3. We need to find out what DEP is
actually measuring.
October 2002
US CMS HCAL at BU
5
HB/HE LED and Laser
•
•
•
•
From Test Beam at CERN in 2002
Nichia blue LED barely excites K27 fluor.
The LED light to HPD is mostly scattered blue
light.
Easy to correct so LED light to HPD should be
very similar to megatile. Use green LED that is
2.5 times brighter. (See K. Johnson talk).
Green LED at 5 volt and 25 nsec should
correspond to over 1 TeV.
October 2002
US CMS HCAL at BU
6
HB/HE LED and Laser
• Basic calibration module design is good.
• Laser distribution has been measured in the
lab with splitters and the correct length of
quartz fibers. Measurements with Pin
Diodes and corrected for HPD.
• QE of Pin Diode 80%, QE of HPD ~10%
with a gain of 2000.
October 2002
US CMS HCAL at BU
7
Laser system
•
1.
2.
3.
4.
Laser to Calorimeter sector (e.g HB+) to
Calibration box to HPD.
337 nm UV. Pin1 = 25pC. Pin2 = 3pC,
HPD = 30 pC.
380 nm with dye laser. Pin1 = 50pC, Pin2
= 6pC, HPD = 60 pC.
UV laser to megatile 4 pC.
Dye Laser to megatile 0.3 pC.
October 2002
US CMS HCAL at BU
8
Progress
• HB Calibration box on hold waiting for
VECSEL connection determination. Most
optical parts completed.
• HE Calibration box, first prototype under
construction (just completed).
• HO Calibration box – box dimensions not
yet specified.
October 2002
US CMS HCAL at BU
9