quartztofmike albrow cms-fp420 april 28 th 2008 quartztof an isochronous & achromatic cerenkov...

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?).


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


nLL

11.))cos(1.(

L

L

n

LL

ct

1

n

LL

ct

1

n

LL

ct

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: 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)


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!


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)


“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


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


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)


Additional Slides


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: 1st simple concept Front section read-out


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

quartztofmike albrow cms-fp420 april 28 th 2008 quartztof an isochronous & achromatic cerenkov...

Documents

fp420 slide

quartztofmike albrow

light prompt

earlier light

light wavefront of z

inner light

lucky light

light lag