21A2 U90 - (White Light) Photochemistry

The optical layout of beamline BL21A2

Gas Cell and Optical Flux

Schematic view of harmonic gas cell filter

Pressure at the chamber of differential pumping with 10 Torr rare gas filled in Gas cell.

(Pressure unit in Torr relative to N2)

1st (R1)1.3 × 10-81.1 × 10-31.4 × 10-32.3 × 10-3
2nd (R2)4.8 × 10-92.1 × 10-71.5 × 10-72.1 × 10-7
3rd (R3)6 × 10-107.3 × 10-91.8 × 10-99.3 × 10-10

Beer-Lambert law plot of photocurrent vs. pressure of Ar in Gas cell.

Beamline pressures dependence on the pressure of Gas cell.

The Beamline photon flux and source flux of BL21A1

The figure shows reflectance of SiC mirrors of BL21A1 and BL21A2. Thus, the photon flux of BL21A2 can be estimated from those data combined with BL21A1 photon flux (upper figure). Roughly, the photon flux of BL21A2 is 40 % in the range 5-10 eV and 88 % in the range 20-50 eV of BL21A1.

Photo-current vs. U9 Gap tuning. The current was measured by Keithley 617 without bias at end-station and gas cell pressure was filled with 1.5 torr Neon gas. Gap dynamic tuning rate was set at 0.05 mm/sec

Optical Parameters
Monochromator none
Mirrors M1 (toroidal), M2 (toroidal)
Method of Focusing (if applicable) toroidal M1 and M2
Beam Size on Sample or Detector (FWHM)1.0 × 2.0 mm2

Photons at Sample

Photon Flux 5 x 1015 photons/sec/200mA at 15 eV
Beam Size beam diameter < 1 mm
Energy Resolving Power2 %
Energy Range 5 ~ 120 eV


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21A2 Home



BL Schedule

Optical Layout




+886-3-578-0281 Ext. 1210

BL Spokesperson

Wu, Yu-Jong (吳宇中)
+886-3-578-0281 Ext. 7211

BL Manager/Local Contact

Chou, Sheng-Lung (周勝隆)
+886-3-578-0281 Ext. 3356


  • IR/Visible/UV/VUV Spectroscopy


  • Molecular science

General Information

  • Source: U90
  • Energy Range: 5~50 ev
  • Focused Spot Size: 1 × 1 mm
  • Status: Operational

National Synchrotron Radiation Research Center

101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu, Taiwan 30076