HBD CDR

Gas System and Monitoring

Craig Woody BNL

DC Upgrades/EC Meeting

March 9, 2005

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 2

Requirements Must deliver very high purity gas to the HBD

• More stringent demands than any other PHENIX gas system (O2, H2O at the few ppm level)• No leaks ( stainless steel, welded gas lines wherever possible) • CF4 is expensive ( recovery system)

Operates reliably with CF4

• CF4 is a highly reactive and corrosive gas (reaction with water produces HF acid, dissociation produces F- ions)• Special concern about compatibility of materials

Must continuously monitor gas • Absorbance due to H2O and O2 can cause loss of photoelectrons

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 3

Proposed HBD Gas System

CF4 output gas collected, compressed, purified and reused

L.Kotchenda

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 4

Gas System Costs Company Name

Purchases Cost

Dwyer Instruments $3 740.00

Tescom $1 100.00

Ashcroft Aprx.$800.00

ADI $2 000.00

RXI $3 930.00

Omega Engineering, Inc $108.00

Peter Paul Electronics Co $1 094.00

Khan $3 500.00

Miller Energy Inc $5 950.00

Asco $169.00

Swagelok $4 021.10

Newark $810.00

Matheson Aprx.$2 500.00

Hastings Instruments Aprx.$4 800.00

Agilent $1 368.00

National Instruments Aprx.$3 490.00

   

  Total $39 380.1Two Racks -~$1500Computer -~$1500500L buffer cost - $2 500.0

The labor cost is $ 15 000 . Total: ~ $60K (without pipes, => + $20K)

L.KotchendaNeeds update with some CF4 compatible components

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 5

Affects of Impurities on VUV TransmissionTransmittance in 36cm of Ar Vs PPM's of O2

0

10

20

30

40

50

60

70

80

90

100

110

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Wavelength [Angstroms]

% T

ran

sm

itta

nc

e [

%]

<1ppm O2

~10ppm O2

~110ppm O2

Transmittance in 36cm of Ar Vs PPM's of H2O

0

10

20

30

40

50

60

70

80

90

100

110

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Wavelength [Angstroms]

% T

ran

smit

tan

ce [

%]

~10ppm H2O

~40ppm H2O

~200ppm H2O

Gas Transmittance

0

10

20

30

40

50

60

70

80

90

100

110

1150 1250 1350 1450 1550 1650 1750

Wavelength [Angstroms]

Ar (99.9980% pure),[O2]=5.6ppm, [H2O]=2.3ppmCF4 (99.9990% pure),[O2]=0.6ppm, [H2O]=19.0ppm

(PMT: R6835)Must maintain careful control of oxygen and water levels

• O2 5 ppm

• H2O 10 ppmB.Azmoun

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 6

Transmittance @ 1450 Angstroms Vs PPM 's of O2 thru 36cm of Ar

0

10

20

30

40

50

60

70

80

90

100

110

0 50 100 150 200 250 300 350 400 450 500 550

[O2] [ppm]

Tran

smitt

ance

@14

50 A

ngst

rom

s

[%]

Data

Calibrated Ar/O2 Mix([O2]=10.3, 50.3ppm nom inal)

From Reference

T = exp-(NLp) = exp-(Kp)

Transmittace @ 1290 Angstroms Vs PPM's of H2O thru 36 cm of Ar

0

10

20

30

40

50

60

70

80

90

100

110

0 50 100 150 200 250 300 350 400 450 500 550 600

[H2O] [ppm ]

Tran

smitt

ance

@ 1

290

Ang

stro

ms

[%]

Data

From Reference

Transmission vs ppm’s of O2 and H2O

B.Azmoun

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 7

i

i

i

iCsIGEMmeshCFiOOHCFiCF

peQETLPPMTLd

nPPMN

)(),,()(

112)(

/

5

542/24

22

4

(i= 1120, 1130,…,2000)

Calculation of Npe vs ppm’s of Gas Impurities (H2O, O2)

B.Azmoun

Cherenkov Yield over 50 cm in CF4 (1)

0

0.5

1

1.5

2

2.5

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Wavelength (Angstroms)

Ng

Transmittance in 50cm of Ar Vs PPM's of O2

0

10

20

30

40

50

60

70

80

90

100

110

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Wavelength [Angstroms]%

Tra

nsm

ittan

ce [%

]

<1ppm O2

~10ppm O2

~110ppm O2

Transmittance in 50cm of Ar Vs PPM's of

H2O

0

10

20

30

40

50

60

70

80

90

100

110

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Wavelength [Angstroms]

% T

ran

sm

itta

nc

e [

%]

~10ppm H2O

~40ppm H2O

~200ppm H2O

(n -

1)

<nCF4> =1.00062

Quantum Efficiency of CsI deposited onto metallic substrate

1

10

100

1080 1280 1480 1680 1880

Wavelength [Angstroms]

QE

[%]

* Data Corrected for Obstruction of Collecting Mesh anode* Data extrapolated from 112-108nm

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 8

Npe vs ppm’s of H2O and O2

Parameters of Calc.* Length of CF4 radiator= 50cm* <n>(CF4)=1.00062* =1 (energy of incident e-)* Integrated over Wavelength Range:108 - 200nm {6.2-11.5eV (CF4 cut-off)}* Corrected for mesh+GEM trans (0.885 x 0.83)* Extrapolated Npe down to 108nm assuming 100% trans. between 112 and 108nm (CsI QE also extrapolated over same range)* Using WIS QE plot: makes insignificant difference compared with BNL measuement

B.Azmoun

Npe Vs PPM's of Gas Impurity

10

15

20

25

30

35

40

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500

PPM's of Impurity

Npe

H2O

O2

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 9

Gas Transmission Monitoring

Measure UV transmission of input gas and output gas of each detector half separately

Movable mirror directs beam down four separate optical paths

Maximize beam intensity so can use CsI vacuum photodiodes for readout (gain stability with nanoamps of photocurrent)

Built mainly from commercial parts (McPherson)

D2 Lamp

Monochromator

Focusing elements

Input gas

Output gas HBD East

Output gas HBD West

Reference

CsIPhotodiodes

MgF2 Windows Gas Cells

MgF2 Windows

Movable Mirror

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 10

CsI QE Monitoring Install UV lamp(s) inside detector

Run detector in reverse bias mode and measure DC current (special calibration mode)

QE monitoring only done rather infrequently (every few weeks ?)

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 11

Additional Slides

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 12

HBD in PHENIX

34 cmRmin = 4.5 cm w/o VTXRmin = 72 cm w/VTX

Rmax = 55 cm w/o VTXRmax = 22 cm w/VTX

Weight ~ 6 kg(< 15 kg total)

84 SHV cables

1 gas inlet (1/2”)1 gas outlet (1”)

per side

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 13

Test of a Triple GEM Detector in PHENIX

55Fe spectrum with Ar/CO2 in Lab

• Triple GEM detector installed close to beam pipe ( R ~ 50 cm) • Detector was sensitive to soft background (thin window)

• Tested using using both Ar/CO2 (70/30) and CF4

• Exhibited no sparking or excessive gain instabilities.

C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05 14

Test of a Triple GEM Detector in PHENIX

55Fe specta with CF4 with full luminosity Au-Au collisions at RHIC

Gain Stability @ Const. Gain

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Run #

Ga

in N

orm

ali

zed

to

La

rge

st

Va

lue

Ar/CO2 (360V)

CF4 (495V)

a

% Res. (FWHM) Vs. Data Run

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Run #

% R

es.

[%

]

Ar/CO2 (70/30)

CF4

LAB

320 V

b

• Detector gain and resolution was stable • Observed some low level background (< 50 e’s) during part of one run - depended strongly on beam conditions. - mostly out of time with beam-beam collisions

Conclusion: There appears to be no fundamental problem with operating a GEM detector close to the beam pipe at RHIC