Beamline Information » Beamline by Number » BL21A1 


Chemical Dynamics Beamline

►Contact Information

If you have any technical concerns, please contact us!

BL21A1 Spokesperson:
Lee, Shih-Huang (, +886-3-578-0281 Ext: 7317)

BL21A1 Beamline Manager:
Chou, Yi-Ming (, +886-3-578-0281 Ext: 3269)

►Technical Information

Operational (general use)

Yes, Since May 1st, 2003.

%Time available (general use)

~ 30%


Unimolecular Photodissociation & Bimolecular Reactive Scattering

Light Source

U9 Undulator, 100 Poles, 9 cm Period Length, 1.28 Tesla

Ring Current (mA)

300 mA

Average Beam Lifetime

Infinite Under NSRRC Top Up Conditions

Energy Range

5 ~ 500 eV (250 nm ~ 2.5 nm)

Available Energy Range Of Fundamental Photons

5 ~ 25 eV (250 nm ~ 50 nm)

Energy Resolution (DE/E)

2.5 x 10E(-2) as an aperture of diameter 3 mm is used. 4.2 x 10E(-2) as an aperture of diameter 7 mm is used

Spot Size

FWHM: 1 mm (H) x 1 mm (V)


Two Toroidal Focusing Mirrors, Water Cooling, Material: SiC



Harmonic Photon Suppressor

Filter Gas: He, Ne, Ar, Kr & Xe @ 10 Torr. Efficiency: I(out)/I(in) ~ 1 x 10E(-4)


~ 1 x 10E(16) Photons/s

Wavelength Min (nm)

50 (limited by the filter gas)

Wavelength Max (nm)

250 (limited by the undulator)

Experimental Station

Crossed Molecular Beam (CMB) Apparatus

Main Parts

Two Rotating Source Chambers, A Reaction Chamber & A Detection Chamber

Rotating Range

-20 – 110 degree

Vacuum Pumps

Turbo-molecular Pumps

Cryo Systems

Liquid-Nitrogen Trap & He Refrigerators

Ultimate Pressure

5 x 10E(-12) Torr At The Ionization Region

Atomic/Molecular Beam

Expanded By An Even-Lavie Valve

Repetition Rate

Typically 200 Hz

Atomic Source

C, N, O & F atoms Generated By Discharge

Beam Diameter

~ 3 mm At The Reaction Region

Beam Speed

Measured With A Chopper Assembly

Reaction-Ionization Distance

100.5 mm

Mass Selection

Quadrupole Mass Filter


Delay-Type Ion Counter

Data Acquisition

Multi-Channel Scaler (Minimal Dewell Time: 100 ns)


248 nm, 193 nm & 157 nm

Measured Quantity

Time-Of-Flight Spectra Of Reaction Products

Beamline Phone Number

886-3-5780281 Ext 1211


►Station Photos


 ►Schematic Of The CMB Machine


 ►Extension Links