About This Project
I study what happens when a laser shines on electrons as they scatter off of atoms. This process is known as laser-assisted free-free scattering, or LAFF for short. In this project I want to find out if LAFF provides a way of generating short bursts of x-rays.
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What is the context of this research?
It is known that an extremely intense/fast laser pulse can knock an electron out of an atom, and then accelerate the electron so it hits the atom it came from and emits an UV or x-ray photon – this process is called high harmonic generation (HHG). In my work, instead of depending on the laser beam to knock out an electron, I provide the electrons using an electron gun. Other than that, it seems that the process that occurs in my experiments is similar to HHG and might therefore produce UV or x-ray photons. I want to measure the extent to which this happens.
What is the significance of this project?
Scientists are just now gaining the ability to produce short, coherent pulses of x-rays using a device that fits on a table top. Current devices utilize high harmonic generation, and are inefficient, complicated, and costly. However, they provide the capability to study an amazing variety of things, from watching chemical reactions as they happen, to determining protein structure. If we find that laser-assisted free-free scattering provides an efficient mechanism for producing x-rays it will open the door to substantially reducing the cost and complexity of future table top x-ray sources.
What are the goals of the project?
We will complete construction of an apparatus for measuring spectra generated by laser-assisted free-free processes. The initial version of the apparatus will combine a vacuum chamber that is meant for doing electron-scattering experiments and a conventional (visible and ultraviolet) spectrometer. We already have both of these items in our lab. Once completed, the apparatus will be used to determine if there is any harmonic content in the light generated by laser-assisted free-free processes. If we find that ultraviolet light is being produced then we will start work on setting up measurements to determine if x-rays are also being produced. Besides being of practical importance, this is also of interest for basic science.
We will be looking for harmonics in the laser beam after it has passed through the region where the electrons and atoms are interacting. The harmonics are expected to be weak, so we need a sensitive detector to measure them. We will use a photomultiplier tube module (costing about $1800) for this purpose. However, even a small portion of the laser beam can seriously damage the detector. So, we need to use harmonic filters to separate the harmonics from the laser beam. The cost for the filters will be about $1,100. We will also need to get the light from the vacuum chamber to the detector. This needs to be done in a way that keeps stray light from entering the detector, and minimizes the loss of light coming from the vacuum chamber. We will use a fiber-optic assembly to do this, which is expected to cost about $1,000.
Meet the Team
I have a bit of an unusual background for a physicist. Before pursuing my Ph.D. I served in the Marine Corps, worked in electronics, and was a systems programmer. My doctoral work was in experimental atomic physics. I studied the scattering of electrons by helium atoms. After that I became interested in learning how a laser beam affects the scattering process. I have been doing experiments on laser assisted electron scattering for the past nine years. So far, I have published three articles [1,2,3] in Physical Review A about these experiments.
The “Discovering a new way to produce x-rays” research by Dr. Bruno deHarak is project associated with the Physics Department of Illinois Wesleyan University (Federal Tax ID 37-0662594), an Illinois nonprofit corporation with federal tax exempt status under Section 501 (c)(3). All donations are tax deductible to the fullest extent of the law. 100% of your donation for this project supports research activities.
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