TMO Layout & Specifications

A review of the current TMO beamline can be found here:  The time-resolved atomic, molecular and optical science instrument at the Linac Coherent Light Source

The time-resolved atomic, molecular and optical science (TMO) instrument at the Linac Coherent Light Source has multiple instruments to enable a wide-range of gas phase experiments. Some beamline components and diagnostics will be placed in the front end enclosure (FEE) as shown in the functional layout below. This hutch features two interaction points IP1 and IP2, where experimental end stations can be installed. IP1 can offer several end station configurations, as detailed below. IP2 is more specializied for the reaction microscope end station called DREAM.   

EndStations

Interaction Point 1 (IP1)

The first KB mirror pair focuses the beam to the first interaction point of the TMO hutch. TMO has several modular endstations which can be installed in IP1.

MBES

The TMO magnetic bottle electron spectrometer (MBES) features a 2.1 m flight tube and an electrostatic lens to retard high-energy photo-electrons, for improved kinetic energy resolution. At the interaction point, an inhomogenous field is created by a permanent magnet. A flat copper plate is attached to the nose cone, which enables the application of a uniform electric field across the interaction region by applying a voltage to the magnet. The flight tube creates a uniform solenoid field to direct electrons to the MCP detector. This detector is coupled to a dual anode which allows for some radial-discrimination of the measured spectrum.
Refs:
Driver et al. in prep.

MBES Spectrometer Properties

MRCO:

This endstation features an angle-resolving array of 16 electron time-of-flight spectrometers, which allow a wide and adjustable energy acceptance window. By interleaving detector retardations, MRCO enables simultaneous angle-resolved spectroscopy of electrons with disparate energies.
Refs:
Walter, P., et al. J. Synchrotron Rad. (2021). 28, 1364-1376

MRCO Spectrometer Properties

cVMI:

The coaxial VMI (cVMI) endstation provides an electron VMI spectrometer where the ionizing laser source propagates along the symmetry axis of the spectrometer. This device provides a unique two-dimensional projection of the three-dimensional electron momentum distribution. The charged particles are detected by an 80 mm microchannel plate coupled to a fast phosphor screen imaged by a fast CCD camera. In addition to the VMI spectrometer, this endstation offers a skimmed molecular beam source.
Refs:
Li, S., Champenois, E. G., Coffee, R., Guo, Z., Hegazy, K., Kamalov, A., Natan, A., O'Neal, J., Osipov, T., Owens, M., Ray, D., Rich, D., Walter, P., Marinelli, A. & Cryan, J. P. (2018). AIP Adv. 8, 115308.

cVMI Spectrometer Properties

dVMI: 

This is a double-sided velocity map imaging spectrometer. We can detect ions and/or electrons allowing for simultaneous measurements of all charged particles generated by photoionization of a single atom/molecule. The spectrometer features a long and short arm. Charged particles in the long arm are detected with a MCP coupled to a quad-anode detector, whereas particles in the short arm are detected with a MCP coupled to a fast phosphor screen imaged by a fast CCD camera. This spectrometer is designed to mount in the multi-purpose LAMP chamber. LAMP features a doubly skimmed molecular beam source.
Refs:
Osipov, T., Bostedt, C., Castagna, J. C., Ferguson, K. R., Bucher, M., Montero, S. C., Swiggers, M. L., Obaid, R., Rolles, D., Rudenko, A., Bozek, J. D. & Berrah, N. (2018). Rev. Sci. Instrum. 89, 035112.

 dual VMI Spectrometer Properties

 KToF:

TMO has a Kaesdorf ETF11B electron time-of-flight spectrometer which can be attached to either the LAMP or cVMI chambers.
Refs: ETF11

KToF Spectrometer Properties

Interaction Point 2 (IP2)

A second pair of KB optics demagnifies the IP1 focal spot to sub-micron size. IP2 features a fixed endstation, the DREAM endstation

DREAM:

The Dynamic REAction Microscope (DREAM) endstation is a cold target recoil ion momentum spectroscopy (COLTRIMS) type spectrometer, which can detect both electrons and ions coincidently. The standard detectors for DREAM are two 120 mm state-of-the-art Hexanode delay-line detectors.
Refs:
Walter, P., Holmes, M., Obaid, R., Amores, L., Cheng, X., Cryan, J. P., Glownia, J. M., Li, X., Lin, M.-F., Ng, M.-L., Robinson, J., Shivaram, N., Yin, J., Fritz, D., James, J., Castagna, J. C., Osipov, T. (2022) Appl. Sci. 12, 10534.

DREAM Spectrometer Properties

Beamline Devices

X-ray Imagers (IM#)

We have several x-ray imagers to measure the beam size and position along the TMO beamline. Each imager features a power meter to measure the beam transmission downstream of every mirror system.

Refs:
Heimann, P. A., Fritz, D., Krzywinski, J., Moeller, S., Nordlund, D., Reid, A., Stefan, P., Walter, P. & Welch, J. (2019b). Proc. SPIE, 11038, 40-43.

Laser In-Coupling (LI1 and LI2)

The TMO hutch has two standard options for in-coupling an external laser pulse. The upstream in-coupling mirror (LI1), features an off-axis mirror which produces a crossing angle of <0.5 deg between the laser pulse and the x-ray propagation. This in-coupling mirror is intended for use with short wavelength (< 800 nm) pulses. Additionally a downstream in-coupling mirror (LI2) features a mirror with a hole to provide co-propagating laser/x-ray pulses. LI2 is intended for long wavelength (>800 nm) laser pulses.

Laser Out-coupling (LI3)

The external laser pulse is out-coupled by an additional mirror (LI3) downstream of the interaction point. This device features diagnostics to facilitate the spatial and temporal alignment of the external laser pulse.

Arrival Time Monitor (ATM1/2)

After each interaction point we have a device to measure the relative arrival time between the external laser pulse and the x-ray pulse.

Wavefront Sensors (PF1/2)

Each interaction point in the TMO hutch is equipped with a wavefront sensor (WFS) to diagnose the focus properties. The sensors make use of the fractional Talbot effect to measure the wavefront. The WFS can be operated in both an averaging mode accepting nearly the total energy available from the FEL, but also in a single-shot mode at reduced (<10 Hz) repetition rate.

Refs:
Liu, Y., Seaberg, M., Feng, Y., Li, K., Ding, Y., Marcus, G., Fritz, D., Shi, X., Grizolli, W., Assoufid, L., Walter, P. & Sakdinawat, A. (2020). J. Synchrotron Rad. 27, 254-261.

Photon Spectrometer (SP1)

Downstream of the first interaction the TMO hutch has a single-shot spectral diagnostic. This device is based on an off-axis Fresnel zone plate, which disperses and focuses the beam to measure the spectral profile. This compact photon spectrometer has a designed resolving power of ~1000 which we have demonstrated at the oxygen K-edge. The resolution is sufficient to resolve the SASE sub-structure as shown in the figure. The single-shot spectrum is recorded to the data set along with other detectors.

Refs:
Larsen, K.A.,  Borne, K., Obaid, R., Kamalov, A., Liu, Y., Cheng, X., James, J., Driver, T., Li, K., Liu, Y., Sakdinawat, A., David, C., Wolf, T.J.A., Cryan, J.P., Walter, P., and Lin, M.F. (2023) Optics Express 31, 35822-35834 

X-Optics

The primary X-ray focusing optics in TMO are pairs of Kirkpatrick-Baez mirrors. Each mirror pair has two reflection zones, one B4C coated and one bare Si, to facilitate a maximum transmission over the energy range covered by TMO. The incident angles with respect to the mirror surface are 14 mrad and 21 mrad for the first and second pair of KB mirrors, respectively. These incident angles allow for an X-ray energy range of 250–2200 eV in the first interaction point (IP1) and an energy range of 250–1400 eV for the second interaction point (IP2). The first pair of mirrors are bendable in a plane-elliptical geometry which enables the foci to be varied along the beamline, and the focus dimension can change from below 1 µm to about 200 µm FWHM. Beyond translating the focus, the first pair can be used to compensate for the aberration of the second pair of mirrors which are not bendable. The average focal length of the KB mirror pairs are 2 m and 0.6 m, respectively.

Refs:
Seaberg, M., Lee, L., Morton, D., Cheng, X., Cryan, J., Curiel, G. I., Dix, B., Fox, K., Hardin, C., Li, K., Li, X., Lin, M.-F., Liu, Y., Montagne, T., Obaid, R., Sakdinawat, A., Whitney, R., Wolf, T., Zhang, L., Fritz, D., Walter, P., Cocco, D. & Ng, M. L. (2022). Synchrotron Radiat. News.

IP1 KBO Mirrors Properties

IP2 KBO Mirror Properties

NEH 1.1 Functional Layout

Download high-res PDF drawing of the functional layout