Report on the Absolute Calibration of the AirLight Experiment · Measure the PMT efficiencies by...

Report on the Absolute Calibration of the AirLight

Experiment

Danays

M. Gonzalez -

7th AFWS, Coimbra

D.M. Gonzalez1, J. Blümer1, K. Daumiller1, H. Klages1, T. Waldenmaier2

1 Karlsruhe Institut für Technologie (KIT), Germany2 Humboldt-Universität

zu

Berlin, Germany

Outline

AirLight

Experiment –

Short Review

Absolute Calibration using the Rayleigh Scattering of a N2

laser beam

System Overview / Components –

Short Review

Si Photodiode Response vs GaAsP Photodiode

Absolute Calibration Setup Improvements

Mechanical System Stability

Scattering inside the instrument

Results with the present setup

Pressure scan

Rayleigh Calibration

Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

Ph

oto

mu

ltiplie

r

Photomultiplier20 cm

PDM

ESM

EDM

Scintillator

Quartz window

Filter

90Sr source

10

cm

•Experimental Setup: Electrons emitted from 90Sr-source produce fluorescence light in gas. This fluorescence is measured by photon detectors around the electron beam [T. Waldenmaier

et al. Astropart.

Phys. (arXiv:0709.1494)]

AirLight

Experimental Setup [T. Waldenmaier]

AirLight

Experiment –

Short Review

• 90Sr, 37 MBq

• Energy Range: 250 keV

–

2 MeV

• Gas: N2

, Dry Air, N2

:O2

mixture (90:10)‏

• Pressure: 2 hPa

–

1000 hPa

• Temperature: ~ 20 0C

• Wavelength Range: 300 –

400 nm

•

Detection: 7 PMTs

with 5 different narrow-band filters and one broad-band (M-UG6 ) filter

•

Fluorescence Yield was absolutely determined with a precision of 15%

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan


Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra


laser beam

Measure the PMT efficiencies by comparison to an energy meter

with an accuracy of ±5%

Rayleigh Scattering theory is used to obtain the precise number of Rayleigh scattered photons:

Raylmol

RayltotLScatt NNN

Scatt

Scattdtected

NNX

Danays

M. Gonzalez -

7th AFWS, Coimbra

Absolute Calibration –

System Overview / Components

PMT

CollimatorLin. Polarizer Filter/4 PlateLin. Pol. Filter (cross

check)Quartz Glass WindowBlack Tube for Collim.

Light SourceLight Source

N2

Laser,

= 337.1 nm

Emax

= 120

J

Pulse Width, FWHM = 3ns

Silicon Energy ProbeSilicon Energy Probe

Laser Probe –

RjP-465

(EminDet

= 500 fJ, EmaxDet

= 250 nJ) ‏

Detection Area = 1.0 cm2

Calibration Accuracy ±

5 %

N2

PMT

Rm

3700

Scattering Volume

PMTs

Si Detector

Beam Splitter

Stepped Density Filter Photonis

XP 2268 and XP2262

Aperture Ring (Ø

=

4.0 cm) Limits the Sensitive Area of the Photocathode.

PMTs

surrounded by Electrostatic Shield (brass tube) ‏

Windows PC Windows PC ––

LabViewLabView

DAQDAQ

Trigger PMT (fast)

Radiometer (slow)

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan

Rayleigh

Calibration

Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

Si vs GaAsP Photodiodes’

Energy Response Measurement @355

nm Nd:YAG

Nd:YAG

Laser –

1064 nmTHG –

355 nm

Circular Stepped Density Filter

Circular Neutral Density Filter

GaAsP

PhotodiodeSi Photodiode

RmSiSi EE

FilterT1

0.69 T Filter Danays

M. Gonzalez -

7th AFWS, Coimbra

Si vs GaAsP Photodiodes’

Energy Response Measurement

Energy response of the Si and GaAsP

photodiodes for different energies (14 pJ

–

4.5 nJ). The response remains linear

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan

Rayleigh

Calibration

Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

Mechanical System Stability Improvement

Linear response of the photodiode


check)Quartz Glass WindowBlack Tube

N2

PMT

Rm

3700

Scatter Box

PMTs

Si Detector

Beam Splitter

Stepped Density Filter Trigger PMT (fast)

Radiometer (slow)

Cross Stage

Splitter Holder

Diffusers

Pinholes

Laser

Chamber

PMT

Danays

M. Gonzalez -

7th AFWS, Coimbra

Si photodiode vs

the trigger PMT responses –

Energy Range: 12 fJ up to 0.6 nJ

Comparison of the photodiode vs

PMT responses for different intensities, using a 337 nm of the N2

laser.

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan

Rayleigh

Calibration

Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

High Scattering inside the instrument

Single photoelectron distribution of one of the PMTs

located around the Laser beam (2.5 pJ

and 948 hPa

of N2

)

Danays

M. Gonzalez -

7th AFWS, Coimbra

Setup Background Improvement



N2

PMT

Rm

3700

Scatter BoxSi Detector

Beam Splitter

Stepped Density Filter Trigger PMT (fast)

Radiometer (slow)

Mechanical setup improvement: Flock Paper, Baffles (Laser shape), Vacuum

Flock Paper, Mechanical Modifications, Vacuum Improvements: removing the flock paper contribution as a trap to the Nitrogen Molecules between measurement sets…

Considerable Reduction of the Background Noise

10 mm

21 mm

2 mm

5 mm

Danays

M. Gonzalez -

7th AFWS, Coimbra

1 mm

1 mm

N2

Setup Background Improvement



Scatter BoxSi Detector

Beam Splitter

Stepped Density Filter

Mechanical setup improvement: Flock Paper (only 1 PMT uncovered), Baffles (backscatter light phd), Tilted phd

40

Flock Paper

Removable Baffle's set

Steel Extension Tube

500

mm

70 m

m

50 mm

Flock Paper, Mechanical Modifications, Vacuum Improvements: removing the flock paper contribution as a trap to the Nitrogen Molecules between measurement sets…

Considerable Reduction of the Background Noise

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan

Rayleigh

Calibration

Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

Measurements

Single photoelectron distribution of one of the PMTs

located around the Laser beam

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan


Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

Pressure Scan

Pressure range from 10-3

h Pa up to 1000 h Pa of Nitrogen

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review






Pressure scan


Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra


Rayleigh scattering cross section

simulation

photons#generatedphotons#detected Rayl

Ωε Geometrical Acceptance

Fluorescence

collQEfilterglassscatt TTNN det

Rayleighcalculated

measured/simulated

XTpY fluodepEN ,,det

simulated

X

X

Raylmol

RayltotLscatt NNN

Number scattered photons reaching the PMT’s iris

2

22

22

24

3

cos116

32124

k

mol

Fnn

Ndd

background corrected

measured

Danays

M. Gonzalez -

7th AFWS, Coimbra

Calibration Factor

Raylmol

RayltotLScatt NNN

015.0

1080.3

1018.9

)pJ 1for (1070.1

226

18

6

Rayl

Rayltot

mol

L

cm

N

N

31068.8 ScattN

19.0Scatt

dtected

NNX

Number scattered photons (Si photodiode)

Detected number photons (PMT) background corrected

...1069.1 3det N

collQEsQuartzGlasTX

Data provided by Photonis: 25.0 collQE

Danays

M. Gonzalez -

7th AFWS, Coimbra

Error Estimation -

Preliminary

Accuracy of energy meter: 5%

Rayleigh cross-section:

3%

Pressure accuracy:

1%

Beam polarization:

0.25%

Acceptance:

2%

Error estimation

(preliminary)

Total uncertainty of calib. factor:

6%

Absolute uncertainty of individual N2

bands:

8% -

11%

Measured by Ulrich et al., in dry air at 1013 hPa

Danays

M. Gonzalez -

7th AFWS, Coimbra

Outline

AirLight

Experiment –

Short Review


laser beam


Short Review

Si Photodiode Response vs

GaAsP

Photodiode





Pressure scan


Outlook

Danays

M. Gonzalez -

7th AFWS, Coimbra

http://www.auger.org/admin/GAP_Notes//GAP2009/GAP2009_128.pdf

Background

from scattering inside the instrument

is understood and considerably reduced

Measurements @ various pressures performed (near vacuum to ambient pressure)

Measurement of PMT with the 337 nm filter for end-to-end calibration

Long tube, vacuum tight and with baffles on top of the chamber, Light trap @ the bottom extension tube, baffles, new phd

angle scan…

new Laser!

Modify the Simulation code: reflectivity of the PMTs, laser shape, geometry of the experiment…

AirLight

absolute calibration using a N2

Discharge Lamp

and a NIST photodiode

(collaboration with Andreas Ulrich and Thomas Heindl)

Status / Outlook

-

done -

to be done started…working on

Danays

M. Gonzalez -

7th AFWS, Coimbra

THANK YOU FOR YOUR ATTENTION!

Danays

M. Gonzalez -

7th AFWS, Coimbra

Report on the Absolute Calibration of the AirLight Experiment · Measure the PMT efficiencies by...

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