| BL 4.0.2 | BL 6.3.1 | Vector Magnet | 2T Magnet |
| Science Highlights |

| Magnetism Workshops at ALS Users’ Meetings |
| BL 4.0.2 Long Term Schedule | BL 6.3.1 Long Term Schedule | Safety @ BL 4.0.2 & 6.3.1





+ Beamline 4.0.2 was the first beamline at the ALS to provide soft x rays of variable polarization using an elliptically polarizing undulator (EPU).

+ The EPU magnet configuration consists of four quadrants. In addition to varying the gap changing the field strength it is possible to move two quadrants along the electron beam direction. This causes a change in field direction (as well as in the field strength) and with that in polarization of the emitted radiation.

BL4.0.2 EPU during installation.

Schematic of EPU magnet configuration.


+EPU parameters:
+ pure permanent magnet device
+ period length of 5 cm, 33 periods
+ device length of 1.85 m
+ minimum gap 14 mm

+The polarization can be switched from left to right
circularly polarized within 2 seconds (17 mm/s) and is under full user control.

+ The minimum energy the device can achieve
depends on the polarization:
+ horizontal polarization: 85 eV
+ vertical polarization: 165 eV
+ circular polarization: 125 eV
+ full range of linear polarization: 210 eV

BL4_monoSchematic of beamline 6.3.1 at the ALS along with the most basic characteristics.



+ The beamline is equipped with a variable-included angle, plane grating monochromator covering the range from 20 eV to 2000 eV.

+ The  resolving power E/dE is 5000 at 870 eV, 7500 at 400 eV, >20,000 at 64 eV.

+ At the transition metal L edges (600 – 1000 eV) the photon flux is about 3x10^12 ph/s/0.1%BW.

+ The spot size at the sample is currently (Dec. 2006) 60 um vertically and 850 um horizontally.







ALS BL 4.0.2 - Technical Specifications









A.T. Young, J. Feng, E. Arenholz, H.A. Padmore, T. Henderson, S. Marks, E. Hoyer, R. Schlueter,
J.B. Kortright, V. Martynov, C. Steier, and G. Portmann
First commissioning results for the elliptically polarizing undulator beamline at the Advanced Light Source
Nucl. Instr. and Meth. A 467-468, 549 (2001).



A.T. Young, E. Arenholz, F. Jun, H. Padmore, S. Marks, R. Schlueter, E. Hoyer, N. Kelez, and
C. Steier

A soft x-ray undulator beamline at the Advanced Light Source with circular and variable linear polarization for the spectroscopy and microscopy of magnetic materials
Surf. Rev. Lett. 9, 549 (2002).



A.T. Young, E. Arenholz, S. Marks, R. Schlueter, C. Steier, H.A. Padmore, A.P. Hitchcock, and
D.G. Castner

Variable linear polarization from an X-ray undulator
J. Synchrotron Rad. 9, 270 (2002).



Contact: Elke Arenholz (