Techniques and Facilities | Advanced Photon Source

Originally constructed and operated as "MHATT-CAT" by a consortium from University of Michigan, Howard University, and Bell Labs-Lucent Technologies, 7ID is now an APS beamline specializing in time-resolved x-ray scattering and spectroscopy. The time structure of the x-ray beam is used to achieve temporal resolution of the x-ray bunch duration (now typically ~200 ps, depending on the fill pattern of the APS-U storage ring). Three experimental hutches allow for a wide variety of experimental setups. A climate-controlled laser lab houses a fs laser while high rep-rate lasers reside in an experimental hutch.

Information on the various hutches:

7ID-B A pink-beam hutch for time-resolved pair distribution function and for imaging fuel sprays and high-pressure liquids
7ID-C Time-resolved x-ray diffraction typically using laser-pump, x-ray probe techniques
7ID-D Time-resolved x-ray nanodiffraction and multimodal imaging

The 7ID beamline is described in the following International Synchrotron Radiation Instrumentation conference proceedings:

Time-Resolved Research at the Advanced Photon Source Beamline 7-ID, Eric M. Dufresne, Bernhard Adams, Dohn A. Arms, Matthieu Chollet, Eric C. Landahl, Yuelin Li, Donald A. Walko, and Jin Wang, AIP Conference Proceedings 1234, 181-184 (2010), DOI: http://dx.doi.org/10.1063/1.3463168
Developments in time-resolved x-ray research at APS beamline 7ID, D. A. Walko, B. W. Adams, G. Doumy, E. M. Dufresne, Yuelin Li, A. M. March, A. R. Sandy, Jin Wang, Haidan Wen, and Yi Zhu, AIP Conference Proceedings 1741, 030048 (2016), DOI: http://dx.doi.org/10.1063/1.4952871

X-ray Characteristics

Energy range (nominal): 4.8-32 keV
X-ray bunch length (24-bunch mode): 90 ps

With the APS-U, the insertion device for 7-ID is an undulator with a period of 2.8 cm and a length of 2.4 meters.

Formerly, the ID line had two insertion devices. The first was an APS Undulator A, with a period of 3.3 cm and length of 2.4 m. A helical superconducting undulator was also installed in January 2018. The on-axis higher harmonics of the HSCU were greatly suppressed compared to a planar device, and the radiation was 100% circularly polarized.

In September 2017, the 7-ID-A high-heat-load monochromator was renovated from water-cooled diamond crystals to two sets of silicon crystals that are indirectly cooled with liquid nitrogen. This upgrade has improved reliability and beam stability by replacing thin, fragile diamond crystals which were quite sensitive to mounting strain. The new monochromator features a choice of Si(111) or Si(311) crystals. Compared to the diamond (111) monochromator, Si(111) has increased the flux by a factor of ~2 and improved the performance of focusing optics. Si(311) provides a narrower energy bandpass and access to much higher x-ray energies.

The 7ID-B hutch can also accept pink-beam radiation.

As part of an APS-Upgrade enhancement, we are adding a white-beam mirror system to reduce the heat load on downstream components. Reflecting surfaces of Si, Rh, and Pt are available.

Laser Characteristics

Spectrum of pulse energies for the various laser excitation sources available at 7ID:

Red circles: Ti:sapphire amplifier and harmonics
Red square: Ti:sapphire oscillator
Black lines: Ti:sapphire-pumped OPA
Blue triangle: Ti:sapphire-derived THz excitation
Green symbols: Duetto MOPA at various repetition rates and harmonics

Femtosecond Laser

Located in separate, climate-controlled laser lab
Transported to 7ID-C and D via in-vacuum overhead transport
Oscillator
- Coherent Micra Ti:Sapphire 300 mW, 20 fs
- 88 MHz repetition rate
- Synchronized to accelerator RF within 250 fs rms
Amplifier
- 800 nm Ti:Sapphire CPA regen (Coherent Legend)
- 2.5 W average power compressed to 50 fs
- 2.5 mJ/pulse at 1 kHz
- Conversion to 400 nm at 15% efficiency
Optical Parametric Amplifier (OPA)
- 100-fs pulses from 200 nm to 20 µm at 1 kHz, with >10 µJ/pulse
Intense THz source
- Peak field ~100 kV/cm, pulse duration 500 fs
- Bandwidth 0.1-2 THz with central wavelength 0.8 THz

High Rep-Rate Laser

Located in 7ID-D experimental hutch
Transportable to 7ID-C via overhead transport
Time-Bandwidth Duetto System
- 10 ps and 130 ps pulse durations
- Repetition rate variable from 54 kHz to 6.52 MHz
- 10 W power at 1064 nm and 54 kHz (185 µJ/pulse)
- Easily converts to higher harmonics 532, 355, and 266 nm
Most efficient use of the high flux/high rep rate of the APS