Microscope for X-ray imaging

[cozkan]

Trying to image a focussed beam on a scintillator (5um Ce:YAG on YAG substrate) at 11keV (photon energy).
NA of the microscope objective used is 0.65 but cannot seem to measure a beam spot size ons cintilaltor smaller than 5um. The expected spot size is 2.5um.

Is this due to the scintillator? Do I need a thinner one? is this because of the higher penetration depth at 11keV? Is it because this is a focussed beam?

Does anyone have any similar experience?

Many thanks in advance

[Ewald]

Hi Cigdem,
some consideration that could maybe help you:
Are you sure that your X-ray spot size is smaller than 5um? Do you have the possibility to check this with another technique?
Have you checked the depth of field of your imaging setup? If it is not smaller than the scintillator thickness, there is no need to reduce the thickness.
Have you considered an influence of the substrate? X-rays could be absorbed by the substrate, reemit and generate fluorescence in the doped part further away from the primary spot?
Cheers,
Friederike

[cozkan]

Hi Friederike,

We didnt have any other way of checking the spot size but knowing the optics well, and having scanned the beam size we know where it stops measuring.
The depth of field of the imaging setup is sufficient and not smaller than the scintillator thickness.
I have considered the influence of the substrate (and literature informs me it is possible) but dont have the substrate separately to test, nor do I have the scintillator on a glass substrate.
Having spoken to Crytur, we think the scintillator is the bottleneck. Have decided to build an x-ray microscope and relax the imaging requirements, instead. Will test the x-ray micropscope hopefully this year.
Thanks for taking the time to respond.
Cheers,
Cigdem

[LorraineBobb]

Hi Cigdem,

I've used a reflective microscope with 25um LuAg in the pinhole camera, but beamsizes would be approx. (sigma_x, sigma_y) =(15um, 45um), 300mA beam, peak energy 25keV.
PERFORMANCE OF A REFLECTIVE MICROSCOPE OBJECTIVE IN AN X-RAY PINHOLE CAMERA, IBIC2018

A few thoughts:

Have you measured the MTF or PSF of the scintillator using a knife-edge? Beamlines tend to have decent targets for this.

Also have you verified the PSF from the optical system (microscope)? Just to sanity check how much PSF comes from the optics?

If you think it's an energy density issue on the scintillator, have you tried attenuating the X-ray beam or using low beam current?

Good luck! ;-)
L.