Monochromator

Improvements and FocusingElke Jackson

Research performed by Elke Jackson, Shannon Lunt, and Yenny Martinez

With the support of Drs. Steven Turley and David Allred

Monochromator OverviewMonochromator Overview

vacuum

vacuum

Octagonal Chamber

XUV Source

Monochromator Chamber

XUV SourceXUV Source Hydrogen gasHydrogen gas High voltageHigh voltage PlasmaPlasma XUV lightXUV light SlitsSlits VacuumVacuum

Octagonal ChamberOctagonal Chamber

Octagonal ChamberOctagonal Chamber

Pinhole

Channeltron Photon

Detector

Stage

θ

2θ

• Pinhole selects beam

• Stage/Detector: θ/2θ

• Channeltron:

Multiplier Tube

ChamberChamber

Entrance Beam

Exit Beam

First Order Diffractions

To XUV Source

To Octagonal Chamber

Entrance Slits Exit Slits

Specular Reflection

Reflective Diffraction Grating

Grating Equation:

mλ = d (sin α + sin β)

Gmλ = (sin α + sin β)

mλ = d cos K sin φ

Reflective Diffraction Grating

Grating Alignment• Mount new grating• Outside alignment

with laser• Inside alignment with

laser– Aligning the laser– Adjusting the grating

• Alignment with source

New grating:• 1200 lines per mm,

twice that of the old grating

• Half the width of the old grating

Reflective Diffraction GratingAdjustments

FocusingFocusing

Detector placementDetector placement Reduce slit width, keeping counts upReduce slit width, keeping counts up 10 micron goal10 micron goal Centered beamCentered beam

Small entrance beam focuses Small entrance beam focuses to small exit beamto small exit beam

Adjust monochromator settings Adjust monochromator settings to find beam through small slitsto find beam through small slits

Slit, adjustable width

Centering beam

Detector Scans at Given Slit Widths

0

100

200

300

400

500

600

700

4

4.2

5

4.5

4.6

4.7

4.8

4.9 5

5.1

5.2

5.3

5.5

5.7

5

angle

co

un

ts/h

alf

se

c

20 um

10 um

30 um

40 um

Focusing:Focusing:Detector scans at given slit Detector scans at given slit widthswidths

• Curve shape does not change with slit size

• Beam centered in slits

Focusing:Focusing:Wavelength scans at given Wavelength scans at given lever arm micrometer settingslever arm micrometer settings

Lever Arm

Lever Arm Adjustment Micrometer

• Adjusting the lever arm micrometer moves the grating

• Maximize counts to the detector around wavelengths of greatest intensity by comparing wavelength scans at various micrometer settings

Focusing:Focusing:Wavelength scans at given Wavelength scans at given lever arm micrometer settingslever arm micrometer settings

Norm alized Averaged Wavelength Scans

00.10.20.30.40.50.60.70.80.9

1

2430.4 2430.8 2431.2 2431.6 2432 2432.4

monochromator wavelength reading

2.52.752.252.42.62.55

Focusing:Focusing:Wavelength scans at given Wavelength scans at given lever arm micrometer settingslever arm micrometer settings

Full Widths at 2/3 Max

0

0.2

0.4

0.6

0.8

1

1.2

1.4

2.2 2.3 2.4 2.5 2.6 2.7 2.8

m icrom eter setting

mo

no

ch

rom

ato

r w

av

ele

ng

th d

iffe

ren

ce

(.5

An

gs

tom

s)

Focusing:Focusing:Wavelength scans at given Wavelength scans at given lever arm micrometer settingslever arm micrometer settings

Peaks of 16,000 counts (2 second intervals)Peaks of 16,000 counts (2 second intervals) Average standard deviation of 112 countsAverage standard deviation of 112 counts

Now:Now: Wavelength scans, lever arm at < 2.25Wavelength scans, lever arm at < 2.25 Similar optimization with cam micrometerSimilar optimization with cam micrometer Place pinhole and locate beamPlace pinhole and locate beam Bug fixes in computer programBug fixes in computer program Stabilize source or determine its riseStabilize source or determine its rise Write new standards of procedure to reflect Write new standards of procedure to reflect

changeschanges