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QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
QUARTZTOFAn isochronous & achromatic Cerenkov Counter
Making Cerenkov light parallel point focusing
Mike Albrow (Fermilab)
New and original design/concept for fast timing Cerenkov counter
Ray-tracing calculations done:Expect > factor 10 more photoelectrons than either GASTOF or QUARTIC Photons arrive promptly (< few ps) at MCP-PMT
Full (wavelength dependent) simulations being done.Needed for [x,y] position dependence over [2mm x 20mm] area.
Two being made for beam tests (July-Aug?).
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
How many photoelectrons (all prompt)?
290~factor 0.804,QUARTZ)(1
1
0028.0)gas,1atmC4F8O(1
1
11.L(cm).90
)(sinL(cm)..90N
2
2
2
2p.e.
n
n
n
c
3 cm quartz ~ 29 x 30cm gas (latter ~ 10 pe.)Difficulty with quartz has been in focusing it.Can have quartz plate e.g. 2mm thick – 45deg concave mirror (proximity focus)which gets ~ 2 x 30 cm gas and is simpler.
QUARTIC design had 64mm quartz in 8 bars, but only few% of light “prompt”Got 3-4 p.e. per bar, say ~ 30 per Quartic
36 mm + 15 mm QUARTZTOF 180 + 75 prompt p.e.
PDG Rule-of-thumb
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
nLL
11.))cos(1.(
L
L
n
LL
ct
1
n
LL
ct
1
n
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1
Geometrical optics: All Cerenkov light from z = 0 to z = Lreaches back plane at same time and parallel to axis.Cone full angle must = Cerenkov angle. Therefore it can be focused to an isochronous point.
Light emitted beyond z = L is refractedback through cone;A conical reflector canmake it also parallel.
Solid Conical Radiator(or half-cone for FP420)
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
.
QUARTZTOF: Dual read-out radiator
Annular plane mirror
Annular plane mirror
Scale
2 cm0 1 cm
R_in ~ 2.7cmR_out ~ 4.0cm
p, z-axis
Wavefront of z = 3.6-5.0 cm light
Wavefront of z = 0 -3.6cm light
Wavefront of z = 3.6-5.0 cm light
Lag = 3.5 cm = 117ps(not shown to scale)
Quartz (fused Silica)or Plexiglas cone.n(shown) = 1.495Θ(Cerenkov) = 48°
Θ(Cone) = 24°
FRONT BACK3.6 cm 1.5 cm
y
x
+/- 1mm flat
Half coneBeam
ScatteredProtons
FRONT VIEW(not to scale)
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
Top View: Optics, schematic
LHC beam
Scattered proton
OPTICAL AXES
LIGHT RAY
LENS
LENSQUARTZ HALF-CONERADIATOR PLANE MIRRORS
(HALF ELLIPSES)
CONICAL SEGMENTMIRROR
MCP-PMT
Note: Reflections shown in horizontal plane, but in LHC will be UP or DOWN or possibly even BOTH
2 MCP-PMTs (DUAL READOUT)Outer Light later than inner light
Focusing schematic (variations possible)Parallel light can be focused to a point!
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
1 dual readout QUARTZTOF (Optical Elements)
MCP#1(front section)
MCP#2(back section)
John Rauch drawings
Focusing lens(front)
Focusing lens(back)
Solid quartzhalf-coneradiator
Half-ellipseannular plane Mirror (back)
Half-ellipseannular plane mirror (front)
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
1 dual readout QUARTZTOF (Optical Elements)
MCP#1(front section)
MCP#2(back section)
John Rauch drawings
Focusing lens(front)
Focusing lens(back)
Solid quartzhalf-coneradiator
Half-ellipseannular plane Mirror (back)
Half-ellipseannular plane mirror (front)
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
“Lucky Light” (chosen by cone angle) focused to central point.Choose RED or UV. All other wavelengths rings, earlier or later.Earlier light retarded with quartz wedge lens (2mm / 10ps) achromatic
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
Photek Microchannel Plate PMT
With focused light can use the best single channel MCP-PMTsHamamatsu or Photek.
TTS (single p.e.) < ~ 30ps100 prompt p.e. < ~ 3ps
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
Plans:
Discuss with collaborators.
Full simulation especially for {x,y} performancevariations, with wavelength dependence ofCerenkov emission, light transmission, reflectionsand QE (MCP-PMT).
Make two units, with >= 2 MCP-PMTs (single channel)together with state-of-art commercial electronics.
Beam tests at Fermilab June (?) – Aug.
I believe < 5ps timing is possible if electronics up to it (25ns)
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
Additional Slides
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
Altuglas International
Will make prototypes in UVT Plexiglas (cheap and easy to machine at FNAL).Similar optical properties. LHC version probably fused silica (Rad Hard)
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
QUARTZTOF: 1st simple concept Front section read-out
QUARTZTOF Mike Albrow CMS-FP420 April 28th 2008
Focusing schematic (variations possible)Parallel light can be focused to a point!
Use 2 MCP-PMTsbecause inner &outer light at differenttimes. Dual Read-Out
QUARTZTOFSide view: PMTs UP or DOWN