Brightness of Horizontal (H5) and Vertical (H1) Cold

SourcesKen Andersen

1011

1012

1013

0 2 4 6 8 10 12

ILL Cold Source Brightnesses

HCS brightness (Ageron measured)

HCS brightness (Calzavara)

VCS Brightness (Ageron calculated)

VCS brightness (Calzavara)

Wavelength (Å)

H1

H5

Extract Brightness from Neutron Measurement Needs end-of-guide position with chopper and

TOF analysisReadily available on H1: Figaro, D17, PF1BNot so readily available on H5 (IN15?)

Propagate backwardsCorrect for attenuation through window

materials etc.Scale using Au-foil measurement

Use spectrum measured on Figaro (H172)

Detector spectrum corrected for chopper opening time

0

5000

1 104

1.5 104

2 104

2.5 104

0

1 106

2 106

3 106

4 106

5 106

0 2 4 6 8 10 12 14

Figaro spectrum

measured

measured*T/ t

lambda (A) time

dis

tan

ce

Δt Δt

Al Bragg edges measured on D17

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Transmission of AG3 Aluminium on D17

75mm AG3 Al

50mm AG3 Al

wavelength (Å)

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80

AG3 Aluminium Transmission on D17

Thickness of AG3 window (mm)

y = exp(-m1*x)

ErrorValue

8.2921e-50.0067182m1

NA4.5788e-5Chisq

NA0.99973R

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80

AG3 Aluminium Transmission on D17

Thickness of AG3 window (mm)

y = exp(-m1*x)

ErrorValue

8.2921e-50.0067182m1

NA4.5788e-5Chisq

NA0.99973R

Al window transmission

2 106

2.5 106

3 106

3.5 106

4 106

4.5 106

5 106

2 2.5 3 3.5 4 4.5 5 5.5 6

Figaro spectrum

lambda (A)

T=0.875

⇒t=20mm

Al window transmission

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Transmission of Al as a function of neutron wavelength

T(75mmAl)T(50mmAl)T(20mmAl) from 75mm dataT(20mmAl) from 50mm data

lambda

0

1 106

2 106

3 106

4 106

5 106

6 106

7 106

0 5 10 15

Figaro spectrum

figspec*T/DTfigspec*(T/DT)/Altrans

lambda (A)

Detector efficiency

lnePP )(0 1

82.0)Å8.1(

b5.4

30

Pp

mml Window thickness = 10mm- half of the total 20mm

Air attenuation

Ageron measurement at 60% humidity

50cm through air

75]Å[04.0]m[ 1

Attenuation through frame-overlap mirror

0.01

0.1

1

0.1 1 10

Inverse attenuation length of single-crystal Si at 300K

measured (Freund)

absorption

used for Figaro data

(Å)

0.7mm Si at 3° angle

Final corrected spectrum

0

1 106

2 106

3 106

4 106

5 106

6 106

7 106

0 5 10 15

Figaro spectrum

figspec*T/DTfigspec*(T/DT)/Altransfigspec*(T/DT)/Altrans/deteff/airtrans/Sitrans

lambda (A)

Flux (

arb

. u

nit

s)

Propagate backwards through guide

0.0001

0.001

0.01

0.1

0 5 10 15 20

Guide transmission

H171 guideFigaro with 5mm slits

wavelength (Å)

1000

104

105

106

107

108

109

106

107

108

109

1010

1011

1012

0 5 10 15 20

Figaro flux

source brightness

wavelength (Å)

outinguide AAT BrightnessFlux

Gold foil measurementAugust 2007after installation of H17

guidesat VS position: entrance

into level C casemateH171 (Figaro)

Φcapt=1.07×1010 n/cm2/sH172 (Granit)

Φcapt=1.57×1010 n/cm2/s

Evaluate capture flux at VS and rescale

dTAA guideoutin Å8.1

BrightnessFlux Capture

109

1010

1011

1012

1013

1014

1 10

Cold Source Brightness

Figaro brightnessAgeron brightness

wavelength (Å)

Comparison of capture fluxes

Capture Flux(n/cm2/s)

Measured Calculated from Ageron

Present calculation

H171 (Figaro) VS 4.24×1010

August 20072.88×1010 (4.24×1010)

H172 (Granit) VS 6.19×1010

August 20074.03×1010 5.98×1010

H172 (Granit) mono 4.4-4.8×1010

April 20083.20×1010 4.63×1010

Spectral flux at Granit monochromator

100

1000

104

105

106

107

108

109

1010

1 10 100

Flux at H172 Granit monochromator

Ageron

from Figaro spectrum

wavelength (Å)

Spectral flux at λ=8.9Å (n/cm2/s/Å)

Previous estimate

(2005-2007)6.4×108

Ageron brightness 4.4×108

Present calculation 5.4×108

Brightnesses of HCS & VCS

1011

1012

1013

0 2 4 6 8 10 12

ILL Cold Source Brightnesses

HCS brightness (Ageron measured)HCS brightness (Calzavara)VCS Brightness (Ageron calculated)VCS brightness (Calzavara)VCS brightness (Figaro)

Wavelength (Å)

SummaryPrevious estimate of 8.9Å flux at Granit was

about rightAgeron VCS brightness is slightly low

needs 50% readjustment in the 1.5-4Å rangeneeds 20% readjustment around 9Å

HCS and VCS brightnesses are probably about the same (within 30%)