Beamline Alignment Quick Reference

Back to X-Ray Microscopy

1) Select x-ray energy:
Calculate scattering angle of Si 111 for desired energy with Bragg law calculator (or approximate Theta ~ asin(1.977084/E keV) )
Bring up alignment motor tab via DCM flag on main beamline screen - DCM soft motors
Drive DCM Theta to the correct Bragg angle for the desired energy
Drive both undulators to the desired energy plus an approximate offset of +0.1keV

NOTES:
i) If DCM theta looks low for the current energy (~2-4 deg) you may need to re-set user offset (current calibrated theta offset = dial + 8.646deg)
ii) Approximate undulator offsets are ~ desired energy +0.1 keV at ~8keV, +0.2keV at 12 keV

2) Scan mirror piezo:
Set slits to

Slit	H Size (mm)	V Size (mm)
PBS	0.2	2
NES	2	2
BDA	2	-

Scan mirror piezo with a scan width of ~2V, ~ 21 points.
Set mirror piezo to the maximum intensity.
NOTES:
i) mirror piezo feedback should be OFF (MIR flag on main beamline screen)
ii) CCD azsol shutter should be set to "manual open" or removed from beam path

3) Scan DCM 2nd crystal roll:
Set slits to

Slit	H Size (mm)	V Size (mm)
PBS	0.2	2
NES	0.2	2
BDA	2	-

Scan DCM Chi2 (roll) with a scan width of ~0.2 mrad, 21 pts, (at least 1 sec of positioner settling time)
Set roll to maximum intensity - correct for backlash.
NOTES:
i) Correct for backlash by driving to first scan point, then to maximum (e.g. after scan drive relative position -0.1, then drive absolute position to max)
ii) Settling time of at least 1 second is necessary for this scan (this axis is UHV picomotor driven in PID)

4) Scan DCM 2nd crystal pitch:
Set slits to

Slit	H Size (mm)	V Size (mm)
PBS	2	2
NES	2	2
BDA	2	-

Find DCM piezo motor via IOCs flag - DCM - motors - motor 1 (or manually enter in scan window 26idbDCM:m1.VAL)
Scan control voltage for DCM piezo tweak with a scan width of ~3V, 21pts.
Set piezo to maximum intensity.
NOTES:
i) DCM feedback should be OFF (DCM flag on main beamline screen)
ii) if voltage is trending out of range (1V<V<9V), set tweak to 4.5V and scan theta2 motion +/- 0.1mrad

5) Scan Undulators:
Scan upstream and downstream undulators with a scan width of 0.5 keV (1 sec settling time), drive to maximum intensity
NOTES:
i) Settling time of at least 1 second is necessary for this scan (possibly more)

6) Optional - scan BDA:
Set slits to

Slit	H Size (mm)	V Size (mm)
PBS	0.2	2
NES	0.2	2
BDA	0.2	-

Scan BDA horizontal center with a scan width of ~0.6mm, 21pts.
Set BDA horizontal center to maximum intensity
Return horizontal BDA width to 2mm for full beam, 0.025mm for horizontally coherent scanning probe beam
NOTES:
i)This scan is optional if BDA is not being used or if the results of the horizontal alignment (steps 2 and 3 above) are similar to previous.