a rich with aerogel for a hadron machine on behalf of the lhcb rich group some results and...

A RICH with Aerogel for a hadron machine

On behalf of the LHCb RICH group

Some results and considerations on: Cerenkov angle resolution from aerogel Index of refraction homogeneity in an aerogel tile

And of Budker and Boreskov Institutes of Novosibirsk

RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi

The RICH of LHCb

p (GeV/c)

radiator Refractive index

2 - 10 Aerogel 1.030

10 – 60 C4F10 1.0014

60 - 160 CF4 1.0005

Momentum

The RICH-1


A RICH with aerogel for an hadron machine is a big challengewith respect to experiments like:HERMES (C resolution ~ 9 mrad measured) or

BELLE (RICH upgrade θC resolution ~ 12 mrad expected)

Because of: exposed to high radiation dose

very high multeplicity and background it is mandatory : photoelectron multeplicity as high as possible angular resolution as small as possible

A RICH with aerogel

RICH-1(aerogel+C4F10)

RICH-2 (CF4)

(Vassily Kandinsky)


AEROGEL as Čerenkov radiator

very light, solid quartz-like structure SiO2 low density around 0.15 g/cm3

refractive index n = 1 + 0.21 transparent in the visible region can be hygroscopic or hydrophobic

LHCb choice

T = A e (-C t /4)

A is the long transmittanceand

C is the clarity coefficient

Photon transmission is described by :

where


C = 0.0045-0.0065 m4 cm-1

T = 35% for 4 cm tile at 400 nm

Boreskov Institute of Catalysis (Novosibirsk)

AEROGEL

Index of refraction:n = 1.03066n = 1.02982

10 x 10 x 4 cm3 tile (2002)

4 cm

8 cm


1 big tile11.6 x 11.6 x 5.5 cm3

successfully produced in 2003 n=1.026 at =400 nm

AEROGEL

C = 0.0057 m4 cm-1

T = 30% for 5 cm at 400 nm


AEROGEL as Čerenkov radiator

Tiles20.0 x 20.0 x 5.1 cm3

successfully produced in 2004 n=1.029-1.031 at =400 nm

C = 0.0060 m4 cm-1

T = 30% at 400 nm


’sfrom 60Co (ISS)

humidityabsorption

protonsfrom IRRAD-1(CERN-PS)

C and T measurements

after bakingthe tile

neutronsfrom IRRAD-2(CERN-PS)

Aerogel ageing tests


Contributions to the angular resolution / :

Č angle resolution

Pixel C/C ~ d/4R (d pixel size, R mirror focal distance)

chromatic dispersion C/C ~ ½ [n/(n-1)] (depends on the

n n(λ) functional behaviour e.g. Sellmeier)

Emission point C/C ~ t sinθC cosθC / L√12 (t rad.thickness, L distance to PD)

Index of refraction C/C ½ [(n-1)/(n-1)]

Tracking C/C depends on precision of tracking

system(+ alignment of optics, optics distortion,…)


The RICH of LHCb

Aerogel properties

ČerenkovAngle precision

Photoelectron yield

L [cm]

n

cmax [mrad]

pthres() [GeV/c]

pthres(K) [GeV/c]

5

1.030

242

0.6

2.0

chrom

[mrad]

pixel

emiss [mrad]

track

[mrad]

total [mrad]

N p.e.

2.1

0.6

0.3

1.4

2.6

6.8


Measurements of with beams

To measure , separation power, N p.e. use:

Beam from CERN-PS 2 – 10 GeV/c (p/p=1%)

Negative : - Positive : + /protons (50 – 70%)

Photodetectors:

4 pad-HPDs produced at CERN

3 pixel-HPD produced by DEP (final PD of LHCb)

Beam:


AEROGEL test beam

with 4 pad-HPD Published in NIMA 519(2004) 493


AEROGEL test beam

Aerogel

thickness

with filter (0.3 mm )

C

no filter

C

4 cm 247.1 5.0246.8 3.1

250.0 5.4248.7 4.0

8 cm 245.4 4.8243.7 3.0

246.8 5.8245.0 3.9

4 cm 6.3 ± 0.7 7.4 ± 0.8

9.7 ± 1.011.5 ± 1.2

8 cm 9.4 ± 1.010.1 ± 1.1

12.2± 1.314.7 ±1.6

RESULTS with 4 pad-HPD

C and

N p.e.

DATA and MONTECARLO

Published in NIMA 519(2004) 493


Aerogel Mirror

AEROGEL test beam

with 3 pixel-HPD


AEROGEL test beam

DATA and MONTECARLO

RESULTS with 3 pixel-HPD

Aerogel

thickness

with filter

C

no filter C

4 cm 237.1 2.8238.1 2.4

238.9 3.3239.1 2.8 N p.e.

9.2 ± 0.8 9.4 ± 1.1

12.8 ± 1.0 14.4 ± 1.6

(preliminary)


Measurements of Čerenkov angle resolution

c from test beam data are typically

about 30% larger than expected

Must understand this disagreement(aerogel description in MC, PD behaviour,…???..)

Another possible contribution to C is a dishomogeneity of

n inside an aerogel tile Measure it with 2 methods

Laser beam (lab) electron beam (Č effect) 500 MeV e- at BTF

Č angle resolution in aerogel


Measurements performed on a 10×10×4.2 cm3 tile with n=1.031 at L=75.8 cm

n with laser beam

y

y

yyt

nyn

tL

yn

y

n

0

dd

d

~0.35 mradn~0.8∙10-4

=543.5 nm


Aerogel

CCD camera

laser


n with laser beam

(n-1)/(n-1)~1.3%

n ≈ 4.6∙10-4 ≈ 1.8 mrad

Result for this tile:


Aerogel Photographic Analysis by Cherenkov Emission

n with e- beam

500 MeV electron beam at the DANE Beam Test Facility (LNF – Frascati) B&W photographic films as photodetectors


n with e- beam Film Mirror

Aerogel

Scan of the aerogel tile:


Mirror Aerogel

e- beam

Film

APACHE

Aerogel ring

N2 ring

• Cherenkov ring width dominated by chromaticity n=n(l)• (n-1)/(n-1)=1% → (θC)=1.17 mrad


Aerogel ring

N2 ring

Hit-by-hit retracking algorithm to build the distribution of the reconstructed C angleResolution: ~0.3 mrad

n with laser beam

DATA


n with laser beam

Result for this tile:

≈ 1.14 mrad (n-1)/(n-1) < 1%

Nitrogen Aerogel


Summary and plans

RICH with aerogel is an essential detector component for b-physics program of LHCb (p/K/p separation in the 2-10 GeV range)

Aerogel for a RICH at LHC is a big challenge: needs excellent optical quality to perform an excellent angular resolution and photoelectron yield

Measured angular resolution not yet completely described by MonteCarlo simulation aerogel simulation needs to be improved to understand fully the intrinsic angular resolution homogeneity in n across a tile must be known


Bern Museum of Art

exhibition ‘La legerete de l’art’ (31 july – 17 august 2003)

(by Veronica Jenssen)


Spare slides


The LHCb detector

Forward single-arm spectrometer

RICH 1RICH 2

YZ view

a rich with aerogel for a hadron machine on behalf of the lhcb rich group some results and...

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