Techniques and Facilities

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 90 ps or less, depending on the fill pattern of the APS 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 white-beam hutch for imaging fuel sprays and high-pressure liquids
  • 7ID-C The laser-pump x-ray diffraction probe station and multimodal imaging station at APS beamline 7ID
  • 7ID-D Time-resolved x-ray spectroscopy and scattering of atoms and molecules

The 7ID beamline is described in the following International Synchrotron Radiation Instrumentation conference proceedings:
X-ray Characteristics
  • 7ID HHL monoEnergy range (nominal): 4.8-32 keV
  • X-ray bunch length (24-bunch mode): 90 ps

Two insertion devices are available at 7ID.  The first is 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 are greatly suppressed compared to a planar device, and the radiation is 100% circularly polarized (but cannot be flipped right to left).

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 white-beam radiation.
Laser Characteristics

7ID laser propertiesSpectrum 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

  • Ti:Sapphire laserLocated 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

  • Duetto in 7ID-DLocated 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