1-ID Insertion Device Information

The insertion device that is currently installed on 1-ID is a standard APS Undulator A. The following information is availiable.

How to scan the undulator.
Actual harmonic energies.
Undulator A Tuning Curves
ANL/APS/TB-3, "Undulator A Characteristics and Specifications" B. Lai, A. Khounsary, R. Savoy, L. Moog, and E. Gluskin (February 1993)
ANL/APS/TB-17, "Undulator A Characteristics and Specifications: Enhanced Capabilities", R. J. Dejus, B. Lai, E. R. Moog, and E. Gluskin (May, 1994).

Dean Haeffner ([email protected]) / 3/26/99

Scanning the Undulator

EPICS 3.13.1 compatible instructions

Insert the PV "1id:ID01_energy" (1id:ID01_gap to scan the gap) into the "Drive" field of the MEDM scan tool. This PV can be found in the xxIDCtrl.adl screen.
Insert the PV "ID01:Energy" into the "Read" field of the MEDM scan tool.
Set the "Gap Deadband" on the undulator control screen to the desired value (1 micron approximately corresponds to 1 eV in 1st harmonic energy.) There is no advantage to setting the deadband to greater than 3 micron and lower settings can considerably slow down the undulator motion.
If you want the energy to read for a particular harmonic, set the "Harmonic Select" field on the undulator control screen.
Enter the desired scan range and step size (or number of steps) and start the scan.

Important Note: Always scan the undulator from large to small gap. The mechanical supports on the undulator are subject to tremendous forces and has some amount of hysteresis. The encoders are calibrated for closing, not opening, the gap. Experimental results have been measured for the Kohzu DCM set to 19.6 keV using both the third and fifth undulator harmonic. Note that these values were for UA#7 prior to the Sept. 98 collision with the storage ring. They will be remeasured and updated as soon as possible.

Measured Harmonic Energies

The energy positions given by the undulator control screen for undulator harmonics are not accurate. The figure below shows the differences between measured and calculated values on for the 1-ID undulator.

Undulator A Tuning Curves

The following is the calculated tuning curve for a standard 3.3-cm period Undulator A.

The following is a measured tuning curve from 1-ID. The monochromator had Si (111) crystals. Note that the data is "raw" and does not include ion chamber efficiencies.