Spherical VLS grating RIXS spectrometers: From basics to the hv 2 concept

Size: px

Start display at page:

Download "Spherical VLS grating RIXS spectrometers: From basics to the hv 2 concept"

Claud Mathews
10 years ago
Views:

1 Spherical VLS grating RIXS spectrometers: From basics to the hv 2 concept Vladimir N. Strocov (ADRESS beamline, Swiss Light Source) Outline: 1. Optical design of spherical VLS grating spectrometers: - maximal resolution and transmission 2. Principles of the hv 2 spectrometer - parallel detection in hv in and hv out

Optical design of spherical VLS grating spectrometers: - maximal resolution

2 Basics of RIXS instrumentation: Spherical VLS grating spectrometer CCD detector γ source α β ω r 2 r 1 spherical VLS grating Spherical VLS grating combining the focusing and energy dispersing actions Workhorse of RIXS instrumentation (ESRF, SLS, DLS, Elettra ) Design goal: maximal resolution and maximal transmission

the focusing and energy dispersing actions Workhorse of RIXS instrumentation

3 1. Optimization at E ref : Spectrometer geometry total linewidth E = ( E ) ( ) 2 aberr + E 2 G aberrations Gaussian broadening Step 1: Entrance and exit arms r 1 and r 2 = L-r 1 to minimize E G E G = S cosα E r1 a0kλ 2 + SE tan E (( β α )/ 2) 2 + D cos β sin γ E r 2a0kλ 2 source slope errors detector Minimization d dr 1 E G = 0 r 1 = D L sin γ cos β cos S α 2 / flexible r 1 : minimal E G or, slightly relaxing E G, small r 1 larger acceptance

+ SE tan E (( β α )/ 2) 2 + D cos β sin γ E r 2a0kλ 2 source slope errors detector Minimization d dr 1 E G = 0 r

4 1. Optimization at E ref : Grating Step 2: Grating parameters a 2 3 ( ω) = a + a ω + a ω + a ω to achieve correct focal plane and minimize E aberr R and a 1 : the focal distance r 2 and focal curve inclination γ (analytically) inclination reduces the effective detector pixel size optimal focal plane inclination a 2 : profile asymmetry (coma) cancellation (numerically) bug in SHADOW fixed in 2010! a 3 : reduction of symmetric broadening (numerically) increase of aberration-free α by a factor >3 E (mev) a 2, a 3 = 0 a 2 0 a 3 =0 optimized a 3 a 2, a α (mrad)

5 Realization: 1500 l/mm spherical VLS grating for the SAXES spectrometer T. Schmitt, V.N.S. et al, J. Electr. Spectr. Relat. Phen., 2013 grating optimized at O 1s edge RIXS with E/ E ~ 10K grating manufactured by Shimadzu FWHM = const towards the full grating illumination of 130 mm a 3 increased aberration-free α by 3

, 2013 grating optimized at O 1s edge RIXS with E/ E ~ 10K grating manufactured

6 TraceVLS: Spectrometer geometry/ spherical VLS grating parameters ray-tracing restricted by the 2D dispersion plane reduced dimensionality + Matlab code vectorization fast optimization loops the optimal grating parameters in a few seconds 3 increase of the Rowland spectrometers acceptance with a 3

Matlab code vectorization fast optimization loops the optimal grating

7 2. Optimization of the spectrometer geometry away from E ref How do we adjust r 1, α, r 2 to keep the best resolution and maximal acceptance? - symmetric-profile conditions E = 530 ev symmetric profile can be maintained for any energy by adjustment of r 1 or α

8 2. Optimization of the spectrometer geometry away from E ref - fixed focal inclination (FI) and maximal acceptance (MA) modes FI mode α ( o ) α (E) r 1 (E) r1 (mm) E (mev) E E G E (ev) E (ev) symmetric profile by different combinations of r 1 and α: the remaining DOF to keep either focal curve inclination or maximal acceptance for any energy MA mode α ( o ) (b) α (E) r 1 (E) E (ev) r1 (mm) E (mev) γ(e) E E G E (ev) γ ( o )

9 TraceVLS software: Spectrometer settings vs energy the focal and symmetric-profile focal α, r 1 and r 2 in a fraction of second

$r 1 and r 2 in a fraction of$

10 fluorescence Prospects of RIXS instrumentation: hv 2 concept crystal field bi-magnons dd-excitations L 3 RIXS of Sr 14 Cu 24 O 41 (J. Schlappa et al) hv in (ev) hv in - hv out (ev) dramatic variations of RIXS intensity with hv in due to intermediate state presently setting hv in and acquisition of I(hv out ) one-by-one full 2D map I(hv in,hv out ) in one shot?

Schlappa et al) hv in (ev) hv in - hv out (ev) dramatic variations of RIXS intensity with

11 Concept of the hv 2 spectrometer: Optical scheme monochromator focal plane hv in V.N.S., J. Synchr. Rad. 17 (2014) 103 plane-elliptical KB refocusers sample imaging in vert plane + dispersion in horiz plane full 2D-map of RIXS intensity in hv in and hv out coordinates (hv 2 spectrometer) critical: extreme refocusing in horiz plane to achieve high source source resolution in hv out ( E x ) out requires XFEL (round beam) or diffraction-limited synchrotron source constant optical length r 1 +r 2 under energy changes: grating pitch + translation to cancel defocus and coma hv in plane-elliptical focuser hv out VLS grating CCD detector

$beam) or diffraction-limited synchrotron source constant optical length r 1 +r 2 under energy changes: grating pitch + translation to cancel defocus and coma$

12 hv 2 spectrometer: Properties monochromator focal plane hv in plane-elliptical KB refocusers sample one-shot XAS data acquisition (TFY) in zero diffr. order sample homogeneity within ~100 µm (not important for liquids and gases) RZP-variant: J. Rehanek et al, J. of Physics: Conf. Series 425 (2013) use of the whole hv in bandwidth 2 orders in efficiency hv in within the XAS linewidth returns identical RIXS spectra 30 in efficiency hv in plane-elliptical focuser hv out VLS grating CCD detector BUT: Extended source incompatible with inclined field of view of grazing-incidence optics resolution degradation beyond hv in ~5 E

Series 425 (2013) 052013 use of the whole hv in bandwidth 2 orders in efficiency hv in within the XAS linewidth returns identical RIXS spectra 30 in

13 Way out: Imaging optics Talk of Joseph Nordgren, D Imaging RIXS Spectrometer Wolter optics delivers flat field of view acceptance of the extended source without resolution degradation

04 1-D Imaging RIXS Spectrometer Wolter optics

14 Wolter imaging optics in hv 2 spectrometer T. Warwick et al, J. Synchr. Rad. 21 (2014) 736 E/ E = 30K in hv out for a 5-m long spectrometer Almost no resolution degradation within ±1 mm Slope errors of the non-spherical optics reduced e.g. by ion milling techniques (talk of F. Siewert)

Almost no resolution degradation within ±1 mm Slope errors of the

15 Summary ADRESS Spherical VLS grating spectrometer optimization of VLS parameters at E ref : a 2 to cancel the lineshape asymmetry; a 3 to minimize broadening at large illuminations maximal aberration-limited α away from E ref : corrections of r 1 and α to maintain the exactly symmetric lineshape; coordinated r 1 and α to maintain, e.g., maximal aberration-limited α (MA mode) flexible r 1, any focal plane inclination, 3 increase of aberration-limited α hv 2 spectrometer imaging/dispersion actions in two orthogonal planes 2D-map of RIXS in one shot of parallel hv in /hv out detection extreme demagnification or imaging Wolter-type optics transmission increase hv in bandwidth up to ~50 diffraction-limited or XFEL source required Future of RIXS instrumentation along the general trend from slits to imaging principles

$RIXS in one shot of parallel hv in /hv out detection extreme demagnification or imaging Wolter-type optics transmission increase hv in bandwidth up to ~50 diffraction-limited or XFEL source required$

16 Acknowledgments Thorsten Schmitt (RIXS science) and Uwe Flechsig (optics) Swiss Light Source, Paul Scherrer Institute Giacomo Ghiringhelli and Lucio Braicovich Politechnico di Milano Ke Jin Zhou Diamond Light Source Gheorghe S. Chiuzbăian Université de Paris 06 Michail Yablonski BESSY and the audience!

Braicovich Politechnico di Milano Ke Jin Zhou Diamond Light Source Gheorghe

Wir schaffen Wissen heute für morgen

Diffractive optics for photon beam diagnostics at hard XFELs Wir schaffen Wissen heute für morgen PSI: SLAC: ESRF: SOLEIL: APS: SACLA: EuroXFEL C. David, S. Rutishauser, P. Karvinen, Y. Kayser, U. Flechsig,