Zone Plate Testing at 1-BM-B Preliminary Results

Michael J. Wojcik, Shashidhara Marathe, Naresh Gandhi Kujala,

2

Testing Goals

Measure focus spot size and efficiency Explore multiple methods for efficiency and focus spot size Image downstream propagation of X-rays from zone plate Explore the possibility of optics characterization with grating interferometry via

wavefront measurement

3

Zone Plate Characterized

3 zone plates fabricated for intermediate stacking. Slightly different focal lengths.~150 um diameter80 nm outer zone width800 nm thick at outer zones

4

Setup

5

Zone Plates

6

Focused X-rays from Zone Plate

• Details of zone plate can be seen in image• Even intensity over line• Nothing blocking zero order light though

pinhole• Image using 500 um separation zone plate• Large background from ambient light during

measurements• ~17% efficiency from ROI statistics in image

7

Pinhole Scans

30 um pinhole at focus was scanned with piezo stage All three zone plates scanned 10 and 20 nm scan steps will be shown Used pin diode downstream for counting, all scans used 1 sec of counting ~14% total focusing efficiency measured with this technique, assuming pinhole is

really 30 um in diameter Efficiency calculated by comparing the counts of zone plate + pinhole versus just

pinhole and assuming flat intensity X-ray field over zone plate Data from scans not fully analyzed, though preliminary results show a FWHM

between 280-350 nm Still understanding what spot size reflects in total system ~200 dark counts versus 10000 for counts through pinhole and 90000 for focused

x-ray counts

8

Pinhole Scans – 300 um Separation Zone Plate

2 um scan20 nm steps

3 um scan10 nm steps

9

Pinhole Scans – 500 um Separation Zone Plate

2 um scan20 nm steps

3 um scan10 nm steps

10

Pinhole Scans – 1 mm Separation Zone Plate

2 um scan20 nm steps

3 um scan10 nm steps

11

Grating Interferometry Image Using Zone Plate

• Shashi is analyzing• Preliminary results suggest not enough

flux for good results• Background might be too large to

accumulate enough useful counts?

12

Problems/Issues to Address

Large background in Andor camera images A central stop to block zero order light Understanding the effect of previously measured 100 nm vibration with 30 Hz

frequency on measurements, namely on line scans Need more light for grating interferometry measurements Finish analyzing focus scans Noisy pinhole scans! Is pinhole best object to use for scanning? Better y-axis control of zone plate position