Wavefront Sensor Testing at APS, April 2023

I’m very proud of some recent work testing our prototype wavefront sensor at hard x-ray wavelengths. We felt very fortunate to have this rare opportunity to test several optical elements, with kind help from the APS team led by Lahsen Assoufid. Prof. Yamauchi made this possible by sharing a new adaptive x-ray mirror made by JTEC for this collaborative work.

Testing the ALS wavefront sensor at the Advanced Photon Source, 29-ID. Wojdyla, Bryant, Goldberg

April 2023

Shi, Wojdyla, Frith, Goldberg, Highland, Bryant at 29-ID, APS

April 2023

“Good Agreement”

Let’s talk about “Good Agreement”

“…good agreement…”
“…remarkably good agreement…”
“…agrees very well with…”

Let’s face it, these phrases have no meaning, and, in my opinion, no place in scientific literature. I’ve used them in papers—before I came to the realization that they have no value. If the agreement is good, tell us how good: use a number, an rms, a percentage, etc. One researcher’s “good agreement” is another’s “failed to converge.” Is your agreement good to within a picometer? or good simply because it’s better than the errors you saw when you collected the first data?

If you use these phrases, you’re not doing as good of a job as you could be doing. Now, there I’ve gone and used the word good, but only because I’m asking you all to do a good job. I can’t be quantitative about that.

Does your data “agree qualitatively,” because the peaks line up, more or less, and the slope is about the same? I might cut some slack if the “good agreement” is coupled somehow to the word “qualitative.”

While we’re at it, let’s remove the words “good” and “bad” from scientific literature in almost every case. Science is not a place for value judgements. Judgements, sure. Opinionsobservations, and speculation, are all okay when marked as such. (“We believe…” is a perfectly legitimate way to start a sentence when you need to tell the reader that you don’t know something for sure.) Your data either agrees with something, or it does not. It agrees with the simulation to within the estimated uncertainty, or it does not. It agrees with the prediction of Dr. X [citation goes here] to within 5%, or it does not. None of us knows what you consider to be good agreement or why, until you give us a number that we can replicate or understand.

So, are we all in agreement? Good.

The Four Laws of Thermodynamics—For Twin Toddlers

Twin toddler boys scoop the last of the chocolate ice cream
  • Zeroth Law You and your brother both have a granola bar, stop complaining.
    If two systems are in thermal equilibrium respectively with a third system, they must be in thermal equilibrium with each other.
  • First Law You’re going to feel better when you poop.
    When energy passes, as work, as heat, or with matter, into or out from a system, its internal energy changes in accord with the law of conservation of energy.
  • Second Law Daddy cannot put the broken banana back together.
    In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases.
  • Third Law It’s impossible to get it clean and keep it clean.
    The entropy of a system approaches a constant value as the temperature approaches zero.

Wikipedia: Laws of Thermodynamics

The SHARP High-NA Actinic Reticle review Program, 2013–

SHARP, the SHARP High-NA Actinic Reticle review Program
SHARP, the SHARP High-NA Actinic Reticle review Program
The SHARP Team 2014
The SHARP Team 2014, Alex Donahue, David Johnson, Markus Benk, Antoine Wojdyla, Kenneth Goldberg
SHARP zone plate array chip
SHARP zone plate array chip, with magnetic features and ruby balls for kinematic positioning
SHARP zone plate Chip array mounted in a kinematic holder
SHARP zone plate Chip array mounted in a kinematic holder
The SHARP Team collecting data
SHARP Team collecting data, David Johnson, Alex Donahue, Chris Anderson, Antoine Wojdyla, Kenneth Goldberg, Markus Benk

Commissioning and aligning the Microfield Exposure Tool (MET), 2003

Commissioning the two-mirror MET, 0.3-NA optic at 13.4-nm wavelength.
Commissioning the MET 0.3-NA, two-mirror optic at 13.4-nm wavelength.
Shown are [Goldberg, Naulleau, Denham]
High-NA null test to calibrate the system geometry. The iamges shows fringes that have a slightly hyberbolic profile due to the planar camera catching a spherical beam.
At high-NA, measurement accuracy is incredibly sensitive to the alignment and geometry. We devised a null-test to provide an absolute measurement of the system geometry for calibration of all other tests.
In a focusing system, the Foucault Test (or Knife-Edge test) is easy to interpret, independent of calibration.
The Foucault Test or (Knife-Edge) test is the easiest to perform, and easiest to interpret. Indepenent of the geometry, the light and dark pattern here reveals the x-derivative of the wavefront error in this moment. The 3rd-order pattern reveals a 4th-order, spherical aberration, which we corrected.
PS/PDI was very difficult to perform owing to the sub-15-nm pinhole sizes. We made it work using a real-time holographic feedback approach that we invented.
Applying our highest-accuracy technique Phase-Shifting Point-Diffraction Interferometry (PS/PDI) was a challenging task since the pinholes were below 15 nm wide and hard to find. We used a real-time holographic feedback approach that we invented, and software I wrote to visualize the data as we aligned the beam. This was a beautiful optic!
Single-grating shearing interferometry at 13.4-nm wavelength.
Shearing interferometry quickly became our favorite approach. Alignment is trivial, the efficiency is high, and the data is easy to analyze. Now, single-grating shearing is used in many beamline applications worldwide.

Measurement of the EUV Test Stand (ETS) 0.1-NA projection lens, 2000

Measurement of the Engineering Test Stand (ETS) at the ALS
Measurement of the Engineering Test Stand (ETS) at ALS Beamline 12.0.1. Shown are Kenneth Goldberg, Jeffrey Bokor, Patrick Naulleau
Sharing interferogram and Fourier transform analysis of the ETS EUV Engineering Test Stand optic
EUV Lateral Shearing Interferometry at 13.4 nm wavelength, and analysis performed with the Fourier Transform method of phase retrieval in orthogonal directions. A single, two-dimensional cross-grating divides the beam. This approach is now sometimes mistakenly called Talbot Interferometry. (Originally, Talbot Interferometry was a two-grating approach.)