Two undulators of period 42 mm with 38 periods each.
The minimun undulator gap is 16 mm but due to power limitations in the front end only one undulator can be set at that value.



The above graphs give peak field, deflection parameter K and Energy of the fundamental as a funtion of gap values. They are rather accurate.

Example:

    typical undulator settings:
    Gap1: 21.0mm. Gap2: 21.17

    Peaks found at 11.2 and 18.69 .

    According to previous graph at 21.0 mm
    Efun = 3.71 keV,
    11.2/3.71 = 3.0 Third Harmonic
    18.69/3.71 = 5.0 Fifth harmonic


    The formulas are: 
             H    = Hoexp(-C.Gap)   Ho=1.956 T   C=0.0759
         K    = 3.923.H
         Efun = 8.224/(1+K^2/2)
The undulators are controlled from IDAPPLI.

Flux Measurements. Examples

The flux has been measured with a calibrated ionisation chamber (OKEN Ref. 0183, Type S194B, thickness 140 mm). The calibration of the chamber has been done by S. Landgrigge from Detectors Group. The obtained results were:



With the above calibration curve the results on the table below were obtained. They refer to the full monochromatic beam, reflected by both mirrors and with a 10 % detuning in the Mostab. The values are normalized to a electron beam current of 100 mA. The ionisation chamber was installed in the Experimental hutch 2 just before the entrance Be window of the UHV diffraction chamber at ~ 45 m from the source. (logbook #22, pg 20).

undulators (gaps in mm ) photon energy (keV) flux (x 10 12 ph/s)
U1: 21.0 ; U2: 21.17 11.2 2.6
  14.5 2.0
  18.7 1.1
 
U1: 16; U2: 30 9.15 0.4
  11.71 0.7
  13.9 1.3
  18.6 1.2