Improved Cherenkov Threshold detectors for

heavy-ions experiment

P. Martinengo,CERN – High-pT Physics at LHC,Tokaj’08

Can we extend the ALICE

PID for hadrons above 5 GeV/c ?

ALICE Club - May 2, 2005Paolo Martinengo

What means “high-pT“ ?

Evolution of the meaning of "high pT"

0

2

4

6

8

10

12

14

1998 2000 2002 2004 2006 2008 2010 2012

Year

"Hig

h p T

" m

eans

> t

han

…

HMPID TDR

U. Wiedemann, Heavy Ions Forum, 10 February 2004

HMPID 3σ p/K limit

Evolution of the meaning of "high pT"

0

2

4

6

8

10

12

14

1998 2000 2002 2004 2006 2008 2010 2012

Year

"Hig

h p T

" m

eans

> t

han

…

HMPID TDR

yesterdayHMPID 3σ p/K limit

Evolution of the meaning of "high pT"

0

2

4

6

8

10

12

14

1998 2000 2002 2004 2006 2008 2010 2012

Year

"Hig

h p T

" m

eans

> t

han

...

HMPID TDR

yesterday

start of LHC

HMPID 3σ p/K limit

Evolution of the meaning of "high pT"

0

2

4

6

8

10

12

14

1998 2000 2002 2004 2006 2008 2010 2012

Year

"Hig

h p T

" m

eans

> t

han

...

HMPID TDR

yesterday

start of LHC

first HI collision ?

HMPID 3σ p/K limit

Conclusion

The HMPIDis an excellent

detector with

a wrong name !

•Identify hadrons with pT ≥ 10 GeV/c track-by-track

•Inclusive measurement, particle yields, especially protons

•Weak identification, i.e. Π,K – protons can be enough

Home work

Material n Πthr(GeV/c)

Kthr(GeV/c)

Pthr(GeV/c)

θmax

(β=1)

Diamond 2.417 0.06 0.25 0.42 65o

Plexiglas 1.488 0.13 0.45 0.85 48o

Vodka 1.363 0.15 0.53 1.01 43o

Beer 1.345 0.15 0.54 1.03 42o

Water 1.332 0.16 0.56 1.07 41o

C6F14 1.29 0.17 0.60 1.13 39o

CF4

(liquid) 1.226 0.19 0.7 1.32 35o

Aerogel 1.05-1.01 0.4-1 1.5-3.5 3-7 18o – 8o

C4F10 1.00140 2.6 9 17 3o

Isobutane 1.00127 3 10 18 2.9o

Argon 1.00059 4 14 27 2o

CF4 (gas) 1.00050 5 16 30 1.8o

Methane 1.00051 5 16 30 1.8o

Air 1.00029 6 20 39 1.4o

Helium 1.000033 17 60 115 0.5o

Nγ (cm-1eV-1) ~ sin2θ(HMPID 1.5 cm liquid C6F14)

~ 2m

•LHCB RICH1 2.4 m•LHCB RICH2 2.0 m •BTeV RICH2 3.0 m•COMPASS > 3.0 m•CBM ~2.5 m

All fixed-target !

“The examples set forth show the great importance which the radiation caused by particles moving at a speed greater than that of light has acquired in experimental physics. Even so, we have not by a long way exhausted all the possibilities for their practical use. There can be no doubt that the usefulness of this radiation will in the future be rapidly extended.”

End of Čerenkov’s Nobel lecture (1958)

ITCImproved Threshold Cherenkov

or

TICThreshold Imaging Cherenkov ?

Nice detector but

the radiator is too long

( 1m for <6> γ’s )

The γ’s yield is too low but compact, simple layoutwell known and mastered technology

θc is not measured but γ’s are associated

to tracks robust w.r.t. high multiplicity, noise

Is it possible to improve the γ’s yield ?

Yes, it is

C4F10

CaF2

IP

HMPID CsI photo-cathode

Quartz cut-off

The HADES RICH

HMPID’s brother, both sons of RD26

1.5 m

Radiator thickness 36 to 65 cm, 12 to 22 γ’s

Momentum Detector resp.

Particle id.

< 3 GeV 0 Who cares?

3 < p < 9 1 Π

0 K,p

9 < p < 17 1 Π,K

0 p

> 17 GeV 1 Who knows ?

C4F10 radiator

Can we do better ?

Yes, we can

CF4

Window less !

CF4 + CsI give 40 γ’s with 50 cm radiator !

CF4 transparent down to 110 nm !

Why not a GEM detector ? (perhaps with the ALTRO R/O)

Nucl. Instrum. Methods Phys. Res., A 535 (2004) 324-329Nucl. Instrum. Methods Phys. Res., A 523 (2004) 345-354

Momentum Detector resp.

Particle id.

< 5 GeV 0 Who cares?

5 < p < 16 1 Π

0 K,p

16 < p < 30 1 Π,K

0 p

> 30 GeV 1 Who knows ?

CF4 radiator

Interesting but not exactly

what we want …

DOUBLE RADIATOR TIC

CaF2 window

C4F10CF4

Window less !

Momentum

C4F10 CF4 Particle id.

< 3 GeV 0 0 Who cares?

3 < p < 5 1 0 Π

5 < p < 9 1 1 Π

9 < p < 16 1 1 Π

1 0 K

0 0 p

16 < p < 30

1 1 Π,K

1 0 p

> 30 GeV 1 1 Who knows?

C4F10 + CF4 radiators

But Čerenkov angles are very similar !( 3o and 1.8o)

CF4C4F10

This would work but it is not elegant

DOUBLE RADIATOR TIC

CaF2 window

C4F10CF4

Window less !

C4F10

CF4

~2.5 cm

~ 10 cm

50 cm + 50 cm

~3 cm

First results from “test beam”

C4F10

C4F10 + CF4

50 cm + 50 cm

# of photons Total charge

Single radiator TIC

C4F10

CaF2

IP

HMPID CsI photo-cathode

SIMULATION

Cherenkov photons

Mirror

chamber

(Giacomo Volpe)

3 GeV/c pions, 189 charged pads 5 GeV/c pions, 366 charged pads

10 GeV/c pions, 564 charged pads

SIMULATION

Blob diameter for C4F10, pad size = 0.8x0.8 cm2

Nikolai Smirnov, Yale Univeristy

Y

Z

X

50 cm

50 cm

AeroGel, 10cm

UV Mirror, spherical shape in ZY

Double sided Read-out planeTriple GEM foils with CsI

CaF2 Window

C4F10 gas

CF4 gas

Particle track & UV photons

R position: 500 cm.Bz: 0.5 T

More ideas…

Simulation for high Pt π+

R

Z

Flat mirrorSpherical mirror

In saturation: <N ph.e.> 25. (C4F10); 30. (CF4)

Double sided Read-out planeTriple GEM foils with CsI

CaF2 Window

UV Mirror, spherical shape in ZY

AeroGel, 10cm

C4F10 gas

CF4 gas

Thick GEM with resistive electrodes (RETGEM)- a fully spark protected detector

A. Di Mauro et al, Presented at the Vienna Conf. on Instrum; to be published in NIM

Geometrical and electrical characteristics:Holes diameter 0.3-0.8 mm, pitch 0.7-1.2 mm,thickness 0.5-2 mm. Resitivity:200-800kΩ/□Kapton type: 100XC10E

30mmor70mm

Principle of operation

Filled symbols-single RETGEM, open symbols –double RETGEMsStars-gain measurements with double RETGEM coated with CsI layer.

15 min continues discharge

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

0 1000 2000 3000

Voltage (V)

Gai

n

Ne

Ar

Ar+CO2

QE~30%at λ=120nm

0

200

400

600

1.00E+00 1.00E+02 1.00E+04 1.00E+06 1.00E+08

Rate (Hz/cm2)

Puls

e am

plitu

de (m

V)

Energy resolution ~30%FWHM for 6 keV

With increase of the rate the amplitude drop, but now discharges

Summary of the main results obtained with kapton RETGEMs

1 mm thick

Fully spark -protected

Discovery:kapton can be coated with CsI and have after high QE

Thick GEMs work even with “unconventional”gas mixtures, i.e. pure Neon or Argon and

even in dry air !

(Vladimir Peskov + Budapest group)

Anything wrong with dry air?

Cheap!Abundant!

Non flammable!~Correct refractive index!

Eigenshaften der Materie in Ihren Aggregatzustanden, 8. Teil Opische Konstanten, 1962

22

CO

22

Ar

24

5

O

22

N

C 0 torr 760air dry 6

10.80

068681.00003.0

82.73

050854.00093.0

003755.0275.2010496.5

12095.0

36.74

053191.07809.0

10)1(

2

2

2

o

n

+ 18 ppm Ne, 5.2 He, 1.5 CH4, 1.14 Kr, 0.5 N2O, 0.5 H2, 0.4 O3, 0.086 Xe

From Olaf Ullaland’s presentation at the CBM

workshop

With a little bit of mixing of CF4 and Ne:Setting (n-1) 106 = 350 at 400 nmgives a mixing ratio of CF4:Ne = 67:33

22

6

10.61

091553.010)1(

nWell described by:

at 0 oC and 760 torr

‘The Dutch Chemist’, c 1780s. Copper engraving by J Boydell after a painting by J Stein.

It may work !

Conclusions (2)

It is possible to extend the PID capability of

ALICE up to 30 GeV/c making use of presently

available technologies at reasonable cost in

a reasonable time

But it is useless if we don’t

find a trigger !