Fast Beam Focusing with the Transparent X-ray Camera – Real-Time Tracking of Beam Shape and Position in-situ

The Transparent X-ray Camera is a beam profilometer that is manufactured using the same single-crystal electronic-grade diamonds as Sydor’s other diamond-based monitors. These diamonds have low x-ray absorption (>90% transmission for x-ray energies greater than 5 keV) for minimal beam and experiment disruption.

The TXC images beam in-situ across a 32 x 32 pixel array in order to track beam shape and position in real time. Each pixel is 60 x 60 μm in size. The TXC offers a solution to spatially resolve x-ray beams with linearity over a wide range of beam flux. This was tested and verified at a synchrotron beamline using a pink beam with 107 to 1016 photons/s flux.

The TXC is an exciting addition to Sydor’s diamond-based monitor suite. It allows for quick identification of beam deviation through imaging and quantifiable flux measurements to make troubleshooting and experiment alignment more efficient. One application that the TXC is particularly useful for is beam focusing using toroidal mirrors.

Toroidal Mirror Focusing: 

Beamlines using toroidal mirrors manipulate the x-ray beam through time-consuming bending, rotation, and manipulation with x-ray optics. This process is used to generate various beam shapes for different experiments, with optimization requiring lengthy, iterative adjustments. In the world of light sources, beam time is a valuable resource, and time should be spent performing experiments, not assessing the beam.

Below is an example of the focusing process being done with a proof-of-concept device in line with a burn paper measurement. This demonstrates the improved imaging precision achieved using a diamond-based monitor vs. that of burn paper. Burn paper also requires movement and replacement of the paper after each measurement. This replacement requires the user to open the x-ray hutch doors and make the replacement which can take up valuable time and adds a frustrating step to the setup of a new experiment.

Using a TXC, and its controller with a built in PID loop, beamline scientists can automatically correct for beam drift, ensuring stability in real time. Replacing manual processes with this automatic feedback decreases the time required before an experiment can begin.

Below is a sequence of frames taken from a video acquired using the TXC prototype at Brookhaven National Laboratory (BNL) at 6 frames per second using the live video option. In TXC Viewer software, users can immediately see the result of focusing a beam with toroidal mirrors.

Evaluation at NSLS-II: Comparing TXC Performance with an ion chamber

In 2022, scientists from Sydor, Stony Brook University, and the X-ray Footprinting (XFP) beamline evaluated the performance of the TXC. In this setup, the XFP pink beam was monitored using an existing ion chamber, with the TXC installed immediately downstream during testing. Measurements were taken with varying beam attenuation and positioning on the TXC. This was performed to evaluate the diamond-based beam profilometer’s dynamic range and compare the quality of the data with that of an ion chamber as a representative of a common beam monitoring solution.

The TXC has three gain stages capable of reading currents ranging from pA to mA per pixel. Aluminum and copper sheets of known thickness were used to attenuate the beam (peak ~10¹⁶ photons/s at ~7 keV). Some key findings included:

• The signal observed by the TXC did not saturate within the measured current ranges; ion chamber signal saturated around 0.1 mA
• The TXC resolved 0.78 nA of total current at high gain with 1.57 mm Cu attenuating the beam to reduce the signal
• The highest sustained total power absorbed by the TXC was over 0.1 W (16 mA) at low gain without any attenuation of the pink beam
• The imaging area of the TXC varies in responsivity by less than 2%

The 16 mA measurement was made with the beam focused in 10% of the detector area and sustained over a 5 minute time period with no sensor degradation and no active cooling. This performance is partly due to the high thermal conductivity of diamond, making it an ideal sensor material.

To observe variation in intensity over the pixel array, the beam was reduced to <100 μm in size using a pinhole. The team was able to generate sensitivity maps of the detector at each pixel position using total currents of 18 nA (high gain) and 17 μA (medium gain). The two signal levels were generated using two different Cu attenuator thicknesses in the beam path.

Using a voltage output on the electronics proportional to current measured by the TXC, software plotted the response uniformity over the full sensor active area. All results showed an extremely uniform response over the diamond’s active area, with an example shown here. In the 17 μA scans, the variation across the entire 32 x 32 sensor array was less than 2%.

The evaluation at NSLS-II demonstrated the robustness of the TXC’s use with unattenuated beam over extended time. The unit showed very uniform response and out-performed the linear range of an ion chamber.

The Transparent X-ray Camera is now commercially available and fully supported by Sydor Technologies.

Shown on the left-hand side is the TXC monitor alongside the TXC Controller. All units are provided with the TXC Viewer software, shown on the right-hand side.

For more information on Beam Monitor product information, please visit https://sydortechnologies.com/x-ray-beam-monitors/ or email info@sydortechnologies.com for a technical consultation with one of our technology experts.