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k. ito 1 JASS2002 Oct 21, 2002 N KEK layout PF-AR PF-2.5GeV Layout of the Photon Factory k. ito 2 JASS2002 Oct 21, 2002 Synchrotron radiation beamlines in the vacuum ultraviolet and soft X-ray region Kenji ITO e-mail: [email protected] Photon Factory, IMSS, KEK, Tsukuba, Ibaraki 305-0801, Japan Introduction Optical elements mirrors geometrical shape reflectivity grating basic understanding geometrical optics ray tracing varied-line spacing grating Monochromators normal incidence type grazing incidence type Summary k. ito 3 JASS2002 Oct 21, 2002 k. ito 4 JASS2002 Oct 21, 2002 What is the role of beamlines for SR usage? 1) conducting SR from the storage ring to the experimental stations 2) shaping SR beam, spatially and energetically, to meet the experimental requirements k. ito 5 JASS2002 Oct 21, 2002 Definition of VUV and SX VUV: vacuum ultraviolet EUV: extreme ultraviolet SX: soft X-ray VUV-SX photons cannot propagate in the atmosphere!!! 1 mm SiO2 100 nm 10 nm VUV IR UV Extreme Ultraviolet 10 eV Be Soft X-rays SiL 1 eV 1 nm 100 eV 0.1 nm 2a0 Hard X-rays CK NK OK 1 keV SiK CuK 10 keV D. Attwood, “Soft X-rays and extreme ultraviolet radiation” (1999) k. ito 6 JASS2002 Oct 21, 2002 VUV-SX beamlines must be kept at ultra-high vacuum (UHV) 1) To facilitate the propagation of the VUV-SX photons 2) Not to disturb the storage ring no mechanically-rigid window is available!!! 3) To protect the optical elements from contamination, oil-free primary pumps are recommended!!! k. ito 7 JASS2002 Oct 21, 2002 Layout of a typical beamline shielding wall branch-beam shutters main beam-shutters X-ray Beamline Hutch SR VUV Beamline Interlock System pre-focusing mirror monochromator post-focusing mirror Construction of a VUV-SX beamline What kinds of measurements are required? Photon energy range Photon flux Beam size Photon band width Polarization Purity Coherence Beamline optics pre-focusing mirrors monochromator post-focusing mirrors Light source bending magnet undulator multipole wiggler This procedure does not work for a multipurpose beamline. k. ito 7 JASS2002 Oct 21, 2002 Optical elements used in the VUV-SX beamlines 1) reflection mirrors as a focussing tool 2) diffraction gratings, zone plates, multilayered mirrors, filters and crystals as dispersion tools monochromators as a beamline system k. ito 9 JASS2002 Oct 21, 2002 k. ito 10 JASS2002 Oct 21, 2002 Mirrors for SR use 1) focusing of VUV-SX light by various shapes of mirror: sphere, cylinder, parabola, paraboloid, ellipse, ellipsoid, toroid, etc 2) for better reflectivity in the VUV-SX region: substrate: SiC, Si, SiO2, metal, other glass coating materials: Au, Pt, Os,… with modern technology: 1-m long mirrors available surface roughness < 0.5 nm in rms slope error < 1 mrad beamspot size Focusing mirrors of spherical shape Astigmatism of spherical mirror k. ito 11 JASS2002 Oct 21, 2002 Aberration of spherical mirror A Rowland O circle B C AO r OB rt 1 1 2 r rt R cos 1 1 2 cos r rs R OC rs focussing plane To avoid astigmatism: Focusing mirrors of toroidal shape source r focus r´ 1 1 2 r r ' R cos sagittal R tangential 1 1 2 cos r r' k. Ito 12 JASS2002 Oct 21, 2002 Parabolic mirrors to avoid aberration In 2D focusing: paraboloidal Y2=4aX a=f cos2 k. Ito 13 JASS2002 Oct 21, 2002 Elliptical mirrors to reduce aberration F1 F2 (X/a)2+(Y/b) 2 =1 For 2D focusing: ellipsoidal shape mirrors k. Ito 14 JASS2002 Oct 21, 2002 k. Ito 15 JASS2002 Oct 21, 2002 Reflectivity of mirrors Rs Rp a 2 b 2 2 s cos cos 2 Rs=Rp2 for 45° a b 2 s cos cos a 2 b 2 2a sin tan sin 2 tan 2 Rs 2 a b 2 2a sin tan sin 2 tan 2 2 2 2a 2 n 2 k 2 sin 2 2b 2 n 2 k 2 sin 2 2 2 2 4n 2 k 2 4n 2 k 2 1 2 1 2 n 2 k 2 sin 2 n 2 k 2 sin 2 Complex refractive index Ñ = n - ik complex dielectric constant complex atomic scattering factor Reflectivity of gold at 21.2 eV k. Ito 16 JASS2002 Oct 21, 2002 1.0 0.8 Reflectivity Rp 0.6 Brewster angle Rs Rp=0 for dielectric material 0.4 0.2 0.0 0 10 20 30 40 50 60 Incidence angle 70 80 90 Atomic scattering factor for Au k. Ito 17 JASS2002 Oct 21, 2002 ~ F f 1 if 2 f1 Z C 2 m a ( )d 2 2 E 0 f 2 ( / 2)CEm a ( ) K 1 i Df1 Df 2 ~ N n ik ~2 ~ N K Henke, Gullikson and Davis, Atomic Data and Neclear Data Tables, 54, 181 (1993) k. Ito 18 JASS2002 Oct 21, 2002 Reflectivity of gold for s-polarization N M5 L3 Mirrors can play the role of low pass filters. 1°=17.45 mrad Henke et al., Atomic and Nuclea Data Tables, 54, 181 (1993) k. Ito 19 JASS2002 Oct 21, 2002 Surface roughness reduces the reflectivity R=R0 exp[-(4s sinf/l)2] s : micro surface roughness in rms <0.5 nm f : glancing angle glancing angle =1 deg 1.0 glancing angle =1 deg 1.0 Reflectivity 0.8 Reflectivity 5 deg 30 deg 0.6 5 deg 0.8 0.6 0.4 0.4 0.2 0.2 0.0 normal incidence 30 deg normal incidence 0 2 4 wavelength (nm) 0.0 0 10 20 30 wavelength (nm) 40 6 50 8 10 k. ito 20 JASS2002 Oct 21, 2002 Gratings as dispersion elements Diffraction grating Zone plate Multi-layered mirror Filters Crystals 1) Introduction 2) Efficiency 3) Geometrical optics ray tracing 4) Varied-line spacing grating k. ito 21 JASS2002 Oct 21, 2002 Equation for diffraction grating I a 2 sin 2 b / l sin sin sin 2 ND / 2 sin 2 D / 2 b / l 2 sin sin 2 a: amplitude of incident light D 2d (sin sin ) l I has maximal values for D=2m. 40 d=5b N=10 30 I ml sin sin d 10 20 10 0 -4 -3 -2 -1 0 m 1 2 3 4 0 -1 0 1 k. ito 22 JASS2002 Oct 21, 2002 Dispersion of diffraction grating sin sin ml d l d cos m Angular dispersion: Reciprocal linear dispersion: l 10 6 d [mm ] cos cos f nm / mm mr '[mm ] q Focal plane q r´ grating f Diffraction efficiency k. ito 23 JASS2002 Oct 21, 2002 ml sin sin d m=2 m=1 m=0 incident light m=-1 m=-2 m>0 positive order inside order m<0 negative order outside order Diffraction efficiency can be calculated by the scalar theory for l/d<<1. Rigorous numerical calculations based on Maxwell equations gives solutions with much better precision. Note that the efficiency strongly depends on the polarization of incident radiation. Blazed grating k. ito 24 JASS2002 Oct 21, 2002 Maximal efficiency can be achieved at b -b=b-. mlbK=2dsinbcosK where blazed wavelength is lbK and deviation angle is 2K= -. b d Calculated by M. Neviere k. Ito 26 JASS2002 Oct 21, 2002 Laminar grating(1) Grating equation i sin+sin=ml/d h d E0=100 cos2(d/2) Em=(400/m22) sin2(d/2) 100 m=0 Efficiency(%) 80 d=(2/l)h(sini+sin) Primary maximum 60 l/d=[2mcosi+(sin)/p] 40 m=1 20 0 0 Efficiency ×(p2/4+m2) where P=h/d 2 4 6 3 10 l/d 8 10 12 Laminar grating(2) k. ito 26 JASS2002 Oct 21, 2002 When the path difference between 1 and 2 is equal to l/2, destructive interference occurs. 1 2 i h(sini+sin)= l/2 h normal incidence: l=4h grazing incidence: l=2h(i+) Suppression of 2nd order!!! Geometrical optics of diffraction gratings(1) k. ito 27 JASS2002 Oct 21, 2002 Fermat’s principle: the pathlength of an actual ray traveling from a point A to a point B takes an extremal or stationary value. dF=0, where F is the pathlength from A to B. F: light path function The red ray meets the grating at a point P(,w,l) on the nth groove, the zeroth groove being assumed to pass through O. Two rays diffracted from the zeroth and nth grooves are reinforced when their path difference is equal to nml. Light path function F=AP+PB+nml AP ( x ) 2 ( w y ) 2 ( l z ) 2 PB ( x' ) 2 ( y' w ) 2 ( z' l ) 2 k. ito 28 JASS2002 Oct 21, 2002 Geometrical optics of diffraction gratings(2) Expansion of F for z=0 and n=1/d 1 1 1 1 F20 w 2 F02 l 2 F30 w 3 F12 wl 2 2 2 2 2 1 1 1 F40 w 4 F22 w 2 l 2 F04 l 4 ..... 8 4 8 F F00 F10 w F00 r r0 ' spherical aberration ml d cos 2 cos cos 2 0 cos 0 r R r0 ' R astigmatism F10 sin sin 0 grating equation F20 defocus in y-direction F02 F30 cos 0 1 cos 1 r R r0 ' R sin r cos 2 cos r R sin 0 r0 ' defocus in z-direction cos 2 0 cos 0 r ' R 0 comma k. ito 29 JASS2002 Oct 21, 2002 Geometrical optics of diffraction gratings(3) Apply Fermat’s principle to F Fij Fij F F F F dF dw dl 0 0, 0 0, 0 w l w l w l Rowland circle Roland mount r = R cos r0’ = R cos0 A r O r0 ´ B C F20 cos 2 cos cos 2 0 cos 0 r R r0 ' R F30 sin r cos 2 cos r R sin 0 r0 ' F20=F30=0 cos 2 0 cos 0 r ' R 0 k. ito 30 JASS2002 Oct 21, 2002 Geometrical optics of diffraction gratings(4) (L, M, N):direction cosine Ray-tracing F AP PB nml F n ( L L' ) ( M M ' ) ml 0 w w w F n ( L L' ) ( N N ' ) ml 0 l l l L' L T n T w w n N ' N ml T l l M ' M ml (L´, M´, N´) 1 T p p 2 eq e 2 2 e 1 w l n n p L M ml N ml w w l l 2 2 n n n 2 n q 2m l M N ( m l ) l w w l k. ito 31 JASS2002 Oct 21, 2002 Geometrical optics of diffraction gratings(5) Equation of image plane: x' cos( 0 f) y' sin( 0 f) r0 ' cos f where x' L' d y' w M ' d z' l N ' d r ' cos f cos( 0 f) w sin( 0 f) d 0 L' cos( 0 f) M ' sin( 0 f) YZ-coordinate on S-plane Y ( y' r0 ' sin 0 ) sec( 0 f ) Z z' Y r0 ' sec 0 secf wf 100 w 2 f 200 l 2 f 020 lzf 011 z 2 f 002 w 3 f 300 wl 2 f 120 wlzf111 wz 2 f 102 O w 4 / R 3 Y r0 ' zg 001 lg 010 w lg 110 wzg101 w 2 lg 210 w 2 zg 201 l 3 g 030 l 2 zg 021 lz 2 f 012 z 3 f 003 O w 4 / R 3 k. ito 32 JASS2002 Oct 21, 2002 Geometrical optics of diffraction gratings(6) S F SOURCE By ray-tracing, it is possible to see 1) how the beam is focused on the slits and at F, 2) how it spreads on the grating, 3) the geometrical through-put. G M Spot diagram at exit slit 0.10 0.05 Y(mm) M S 0.00 -0.05 -0.10 -0.8 -0.4 0.0 Z(mm) 0.4 0.8 k. ito 33 JASS2002 Oct 21, 2002 Geometrical optics of diffraction gratings(7) Analytical expression for spot diagrams Y r0 ' sec 0 secf wf 100 w 2 f 200 l 2 f 020 lzf 011 z f 002 w f 300 wl f 120 wlzf111 wz f 102 2 3 2 2 w4 O 3 R Z r0 ' zg 001 lg 010 w lg 110 wzg101 w 2 lg 210 w 2 zg 201 l g 030 l zg 021 lz f 012 z f 003 3 2 2 3 w4 O 3 R Analytical merit function: Q Q Q l i i 1 i WLH 2 (Y Y ) dwdldz m Z WLH 2 dwdldz Optimization of design parameters so as to minimize Q, where m is a weight function. Triple integrals have to be done over the grating surface. Note that Y and Z are dependent on li (i=1, 2, …N). Masui and Namioka, JOSA, 16, 2253 (1999) Geometrical optics of diffraction gratings(8) k. ito 34 JASS2002 Oct 21, 2002 Hybrid design method : Koike and Namioka, JESRP, 80, 303 (1996) Yn ( w n , l n , z n ) f ijk w ni l nj z nk n Z n ( w n , l n , z n ) gijk w ni l nj z nk n Ray-tracing of 18 rays determines fijk’s and gijk’s by solving simultaneous equations. Optimization process using the merit function in the same manner as before. Ray-tracing program is available at http://www.xraylith.wisc.edu/shadow/shadow.html k. ito 35 JASS2002 Oct 21, 2002 Varied line spacing gratings (1) Groove function 1 nw , l s w n20 w 2 n02 l 2 n30 w 3 n12 wl 2 2 1 n40 w 4 2n22 w 2 l 2 n04 l 4 ... 8 Effective grating constant nw , l s 1/ w w l 0 sin+sin=l/s =1 for mechanically ruled grating =s/l0 for holographic grating s Varied line spacing gratings (2) k. ito 36 JASS2002 Oct 21, 2002 HG´70 HG´90 n20 TC TD , n30 n40 TC sin TD sin d , rC rD 4TC sin 2 rC 2 Namioka and Koike, Appl. Opt., 34, 2180 (1995) n02 SC S D n12 SC sin S D sin d rC rD SC S D 4TD sin 2 d TC TD 2 rC rD R2 rD 2 2 ..... cos 2 cos TC , rC R SC 1 cos , rC R cos 2 d cos d TD rD R SD 1 cos d rD R Monochromators in the VUV-SX region for SR use (1) k. ito 37 JASS2002 Oct 21, 2002 Normal incidence monochromators M. Koike, “Normal incidence monochromators and spectrometers” in J.A.R. Samson and D.L. Ederer Eds., “Vacuum Ultraviolet Spectroscopy II in Experimental Methods in Physical Sciences” Vol. 32, (Academic Press, New York, 1998, Chapter 1, pp. 1-20 review (A) Seya-Namioka type monochromator (B) Pseudo Rowland mount monochromator K. Ito, Y. Morioka, M. Ukai, N. Kouchi, Y. Hatano and T. Hayaishi, RSI, 66, 2119 (1995) (C) Eagle type monochromator 1) 6.65-m Eagle at BL-12B of the Photon Factory K. Ito, T. Namioka, Y. Morioka, T. Sasaki, H. Noda, K. Goto, T. Katayama and M. Koike, Appl. Opt., 25, 837-847 (1986) K. Ito and T. Namioka, Rev. Sci. Instr., 60, 1573-1578 (1989) K. Ito, K. Maeda, Y. Morioka and T. Namioka, Appl. Opt., 28, 1813-1817 (1989) 2) undulator based 6.65-m Eagle at BL9.02 of ALS M. Koike, P. Heimann, A. Kung, T. Namioka, R. DiGennaro, B. Gee and N. Yu, NIM, A347, 282 (1994) A.G. Suits, P. Heimann, X. Yang, M. Evans, C.W. Hsu, K. Lu, Y.T. Lee and A.H. Kung, RSI, 66, 4841 (1995) D.A. Mossessian, P. Heimann, E. Gullikson, R.K. Kaza, J. Chin and J. Arke, NIM, A347, 244 (1994) 3) 6.65-m Eagle with varibale polarization undulator at SU5 of LURE L. Nahon, B. Lagarde, F. Polack, C. Alcaraz, O. Dutuit, M. Vervloet and K. Ito, NIM, A404, 418-429 (1998) K. Ito, B. Lagarde, F. Polack, C. Alcaraz and L. Nahon, J. Synchrotron Rad., 5, 839-841 (1998) L. Nahon, C. Alcaraz, J-J. Marlats, B. Lagarde, F. Polack, R. Thissen, D. Lepere and K. Ito, RSI, 72, 1320 (2001) Seya-Namioka monochromator (1) 2 I 200 F200 d k. ito 38 JASS2002 Oct 21, 2002 2 1 I 200 I 200 I 200 0, 0, 0 r r ' K R/r=1.220527 R/r’=1.216931 2K=69.44° Seya-Namioka monochromator (2) k. Ito 39 JASS2002 Oct 21, 2002 1000 rays, generated from the entrance slit 10mm long, hitting the 1800-grooves/mm grating with 100(W)60(H) mm2 : from Koike’s review conventional grating holographic grating recorded with a spherical wave front holographic grating recorded with an aspherical wave front E/DE3600 VLS grating with straight grooves E/DE3104 Through put: 23% Pseudo Rowland mount monochromator Robin-Romand mount k. ito 40 JASS2002 Oct 21, 2002 toroidal mirror plane mirror toroidal mirror plane mirror spherical grating of R=3m K. Ito, Y. Morioka, M. Ukai, N. Kouchi, Y. Hatano and T. Hayaishi, RSI, 66, 2119 (1995 Pseudo Rowland mount monochromator F20 k. ito 41 JASS2002 Oct 21, 2002 cos 2 cos cos 2 cos r R r' R Dth is calculated by F20=0. 2 and d are chosen so that 200nm D rr D th 2 is minimized. l 30nm K. Ito, Y. Morioka, M. Ukai, N. Kouchi, Y. Hatano and T. Hayaishi, RSI, 66, 2119 (1995) With a 2400-l/mm grating, E/DE3104 can be attained. Off-plane Eagle (1) k. ito 42 JASS2002 Oct 21, 2002 6.65-m off-plane Eagle spectrograph installed at the PF in 1983 k. ito 43 JASS2002 Oct 21, 2002 Off-plane Eagle (2) 0.1nm 0.1nm Photographic Photoelectric Off-plane Eagle (3) ALS k. ito 44 JASS2002 Oct 21, 2002 Absorbed power density of M1 and M2 are 10.4 and 7.6 W/cm2. M1: spherical M2: toroidal M4: cylindrical M5: cylindrical M6: toroidal Koike, Heimann, Kung, Namioka, DiGennaro, Gee and Yu, NIM, A347, 282 (1994) k. ito 45 JASS2002 Oct 21, 2002 Off-plane Eagle (4) VUV high-resolution beamlineAutoionization spectrum of neon (4300 l/mm grating) with variable polarization at SU5 of SACO (LURE) 20x10 3 Slits 20 12d' mm : FWHM (raw) = 0.22 meV R ~ 97000 140 Slits : 10 mm FWHM (raw) = 0.184 meV R ~ 117000 120 ion yield (counts/sec) 13d' 18s' 100 80 60 40 10 20 14s' 0 21.6116 + Ne Ion Yield (counts/sec) 15 21.6118 21.6120 photon energy (eV) 5 2 P 3/2 39s' 0 21.56 21.58 21.60 21.62 21.64 21.66 Photon energy (eV) With a 4300-l/mm grating, E/DE1.2105 can be attained. Nahon, Alcaraz, Marlats, Lagarde, Polack, Thissen, Lepere and K. Ito, RSI, 72, 1320 (2001) Monochromators in the VUV-SX region for SR use (2) k. ito 46 JASS2002 Oct 21, 2002 Grazing incidence monochromators (A) Spherical grating monochromator (SGM) or Dragon C.T. Chen, NIM, A256, 595 (1987); C.T. Chen and F. Sette, RSI, 60, 1616 (1989). (B) SX700 (PGM, elliptical mirror) and modified SX700 H. Petersen, Opt. Com., 40, 402 (1982); H.A. Padmore, RSI, 60, 1608 (1989); H. Petersen et al., RSI, 66, 1777 (1995). (C) Monk-Gillieson type monochromator M. Hettrick et al., Appl. Opt., 27, 200 (1988); M. Koike and T. Namioka, RSI, 66, 2114 (1995). (D) Harada type monochromator (PGM) T. Harada, M. Itou and T. Kita, Proc. SPIE, 503, 114 (1984); M. Itou, T. Harada and T. Kita, Appl. Opt., 28, 146 (1989). (E) Grasshopper monochromator: Rowland mount F.C. Brown et al., NIM, 152, 73 (1978); F. Senf et al., RSI, 63, 1326 (1992). SGM at the BL-16B of the PF (1) Change the exit-slit position to satisfy the condition of F20=0 Shigemasa et al., JSR, 5, 772 (1998) k. ito 47 JASS2002 Oct 21, 2002 k. ito 48 JASS2002 Oct 21, 2002 SGM at the BL-16B of the PF (2) N2 Theoretical estimation for resolving power Ar Shigemasa et al., JSR, 5, 772 (1998) k. ito 49 JASS2002 Oct 21, 2002 SX-700 H. Petersen, Opt. Com., 40, 402 (1982) F20 cos 2 cos cos 2 cos r R r' R F20=0 with R= r r' cos 2 cos 2 r ' C C=2.25 high grating efficiency rotation tilting or rotation+translation Modified SX-700 on-blaze type monochromator k. ito 50 JASS2002 Oct 21, 2002 Padmore, RSI, 60, 1608 (1989); Petersen et al., RSI, 66, 1777 (1995). M. Fijuisawa, private communication Monk-Gillieson type monochromator r VLS plane grating k. ito 51 JASS2002 Oct 21, 2002 Virtual image point Source Spherical mirror r´ Spectral image point cos 2 cos cos 2 cos mn 20l Defocus term : F20 r R r' R s R=, =1 and m=+1 cos 2 cos 2 n20l F20=0 at two wavelengths l1 and l2 F20 r r' s F30 and F40 can be taken into account, however, it is difficult to control. Hettrick et al., Appl. Opt., 27, 200 (1988); Koike and Namioka, RSI, 66, 2114 (1995). BL-11A (1) k. ito 52 JASS2002 Oct 21, 2002 Kirkpatrick Baez optics r=-r´ F20=0 at zeroth order and 500 eV facilitate the optical adjustment Amemiya, Kitajima, Ohota and Ito, JSR, 3, 282 (1996); Kitajima, Amemiya, Yonamoto Ohta, Kikuchi, Kosuge, Toyoshima and Ito, JSR, 5, 729 (1998); Kitajima, Yonamoto, Amemiya, Tsukabayashi, Ohta and Ito, JESRP, 101-103, 927 (1999). k. ito 53 JASS2002 Oct 21, 2002 BL-11A (2) transmission k. ito 54 JASS2002 Oct 21, 2002 slit widths vs. resolution/flux BL-11A (3) N2 absorption Other important points in the construction of VUV-SX beamlines (1) k. ito 55 JASS2002 Oct 21, 2002 Hardware design Wavelength-scanning mechanism in monochromator: the precision of grating rotation is in the order of 1/100 sec. In-situ adjustment of optical elements, such as rotations and translation. Enclosing the important parts in a temperature controlled booth. Isolation of optical elements Optical elements or optical benches are well isolated from mechanical vibrations caused by ventilators, mechanical pumps, and so on. An ideal beamline is installed on a massive concrete base. Other important points in the construction of VUV-SX beamlines (2) k. ito 56 JASS2002 Oct 21, 2002 Installing beamlines Anticipate how to align beamlines in its design stage. Convenient tools for beamline alignment: theodolites and auto-levels with a telescope and a laser Optical alignment VUV-SX photons are not visible!!! Beam position monitors such as fluorescent screens, photodiodes, and wire monitors are needed. Other important points in the construction of VUV-SX beamlines (3) k. ito 57 JASS2002 Oct 21, 2002 Heat load on optical elements Cooling system For VUV-SX beamlines, direct cooling is difficult! In-Ga alloy is used for better thermal contact between mirrors/gratings and their water cooled holders. Entrance slits are often required to be cooled. Thermal distortion Selecting materials with small value for /k as substrate of mirrors and gratings. SiC and Si are favored. Simulation by ANSYS Other important points in the construction of VUV-SX beamlines (4) k. ito 58 JASS2002 Oct 21, 2002 Specification of mirrors and gratings Consult the makers about the micro roughness, slope error, and groove density, of optical elements, for which the beamline performance is strongly dependent. Vacuum technology Vacuum technology is well established to obtain 10-8 Pa (10-10 Torr). Clean vacuum is obtained by oil-free primary pumps. Contamination of optical elements. cleaning with O2 discharge and UV-lamp. Other important points in the construction of VUV-SX beamlines (5) k. ito 59 JASS2002 Oct 21, 2002 Control systems of beamline PC-base control system for the monochromator including the interface boards for stepping motors and encoders Beam channel? Beamline interlock system to protect the experimentalists from radiation hazards and to avoid vacuum problems Characterization of beamlines Photon flux, resolving power, purity of light, Reproducibility of the wavelength scanning Fluctuation of the beam position on the entrance slit Other important points in the construction of VUV-SX beamlines (6) Safety Radiation safety Gamma-ray stopper downstream of the first mirror, which might be installed inside a cage Flammable and toxic gases Gas duct with a gas detection system Exhaust steam from rotary pumps k. ito 60 JASS2002 Oct 21, 2002