Cryogenic Liquid Jets for High Repetition Rate Discovery Science
May 9th, 2020
This protocol presents the operation and principles of micron-scale cylindrical and planar cryogenic liquid jets. Until now, this system has been used as a high repetition rate target in laser-plasma experiments. Anticipated cross-disciplinary applications range from laboratory astrophysics to material science, and eventually next-generation particle accelerators.
The system described in this protocol has led to a high impact results in proton and ion beam acceleration. Future applications of this system will explore laboratory astrophysics, material science, and the next generation of particle accelerators, leading to peak powers of the order of gigawatts High repetition rate laser has created a need for continuous target. Hydrogen target, in particular, have attractive properties for laser ion acceleration, leading to energetic, pure proton beams.
Christopher Schoenwaelder, a PhD student for my laboratory, will be demonstrating in the procedure All preparation and assembly of the cryogenic source components should be performed in a clean environment, with the appropriate clean room clothing. Begin by using indirect ultrasonic cleaning to remove contaminants from the cryogenic source components. Fill a sonicator with distilled water and add a surfactant to reduce the surface tension.
Place cryogenic source parts in individual glass beakers, fully submerge them in electronics grade isopropanol, and loosely cover the beakers with aluminum foil to reduce evaporation and prevent contamination. Place the beakers in the cleaning basket or a beaker stand in the sonicator, making sure that they do not touch the bottom of the sonicator. Activate the sonicator for 60 minutes, then inspect the isopropanol using a bright white light for suspended particles or residue.
If particles are visible, rinse the parts with clean isopropanol and replace the isopropanol bath. Sonicate in cycles of 60 minutes until no particles or residue are visible. When finished, place the parts on a covered, clean surface to desiccate for a minimum of 30 minutes before assembly.
Repeat the cleaning process for the stainless steel filter, source cap, ferrule, and assembly screws. Cut a piece of indium to maximally cover the junction between the cryogenic source body and the cold finger of the cryostat. Then, place it on the cryogenic source and hold it flush with the cold finger of the cryostat.
Tighten the retaining screws, ensuring the indium remains flat to establish a thermal seal between the components. Do not overtighten, as the copper threads are easily damaged. Screw the threaded stainless steel filter onto the cryogenic source flange.
Place an indium gasket on the source flange and attach the source flange to the cryogenic source body using the flange screws. Then, tighten the screws diagonally instead of sequentially around the circumference. Place the ferrule inside the cap.
Then, use clean tweezers to place the aperture inside the ferrule. Tap the cap to center the aperture in the ferrule. Drop an indium ring on top of the aperture.
Then, tap the edge of the cap again to center the indium ring on the aperture. Hand-tighten the cap onto the source flange until minimal resistance is detected. Derestrict the flow rate on the mass flow controller by increasing the set point to 500 standard cubic centimeters per minute and setting the gas pressure to approximately 50 PSI gauge on the pressure regulator.
Use a wrench to tighten the aperture a few degrees at a time until the flow rate begins to decrease. Check the leak rate at the top of the cap with the high sensitivity leak detector and stop tightening when the measured leak rate stops decreasing. Disable the temperature ramp and change the set point temperature to well below the theoretical vapor liquid phase transition temperature.
At the onset of liquefaction, increase the helium flow for additional cooling power to quickly pass through the phase transition. As the reservoir becomes fully liquified, a mixture of gas and liquid will initially spray from the aperture and sequentially transition into a continuous jet. Use high magnification shadowgraphy with pulsed sub nanosecond delumination to visualize the jet stability and laminarity.
If the experiment has a predetermined location for the sample, translate the cryogenic source using a multi-axis manipulator on the cryostat flange or motorized push pin actuators in the vacuum chamber. Optimize the PID parameters and helium flow to ensure that the temperature stability is better than plus or minus 0.02 Kelvin. Note that the overall stability of the jet strongly depends on the vacuum chamber pressure, gas backing pressure, and temperature.
High magnification shadowgraphs are used to assess laminarity, positioning jitter, and long-term stability during jet operation. It is critical to use pulsed sub nanosecond illumination to record an instantaneous image of the jet so that the jet motion does not blur surface irregularities or turbulence. A study of the spatial jitter of a 2 by 20 micrometer hydrogen jet as a function of distance from the aperture was performed during a single test over several hours.
The positioning jitter for each data point was calculated from 49 images recorded at 10 hertz. The jet position was determined relative to a fixed reference position. The normalized histograms of the jet position at 23 millimeters are shown as an example.
Typical system observables during liquefying and jet operation of a 4 by 20 micrometer cryogenic deuterium jet are shown here. Careful monitoring of the temperature, flow, sample backing pressure, and vacuum pressures allows the operator to quickly identify any irregularities and react accordingly. Typical operation parameters are summarized here.
Once the optimal parameters are identified for a given gas and aperture type, the resulting jet is highly reproducible. Any deviations in the aperture require reoptimization starting from the previously identified values. When following this protocol, is important to notice that sudden changes in pressure or temperature can rapidly vaporize the liquid hydrogen in the reservoir.
To prevent vacuum system failure, the operator should restrict the gas flow and isolate sensitive hardware. The system can also be extended to other aperture geometries and sample gases. Among other things, heavier elements can be used to study fundamental plasma processes such as ion acoustic waves or the transition to one phase of matter, a state that is expected to exist in the interior of gas giants and exoplanets.
High brightness ion beams from this target system are used to generate a directional high flux neutron beam. This technique has paved the way for non-destructive inspection of materials and may contribute to studies of nucleosynthesis in the laboratory.
Overview
This protocol details the operation and principles of micron-scale cylindrical and planar cryogenic liquid jets, which have been utilized as high repetition rate targets in laser-plasma experiments. The anticipated applications span laboratory astrophysics, material science, and next-generation particle accelerators.
Key Study Components
Area of Science
- Laser-plasma experiments
- Material science
- Laboratory astrophysics
Background
- High repetition rate lasers necessitate continuous targets.
- Hydrogen targets exhibit favorable properties for laser ion acceleration.
- Proton and ion beam acceleration has shown significant results.
- Future applications include advancements in particle accelerators.
Purpose of Study
- To demonstrate the assembly and operation of cryogenic liquid jets.
- To explore the stability and laminarity of the jets.
- To optimize parameters for reproducible jet formation.
Methods Used
- Ultrasonic cleaning of cryogenic source components.
- Assembly of components in a clean environment.
- Use of high magnification shadowgraphy for jet visualization.
- Monitoring of temperature, flow, and pressure during operation.
Main Results
- Successful creation of continuous cryogenic jets.
- Demonstrated reproducibility of jet parameters.
- Identified critical factors affecting jet stability.
- Provided insights into the behavior of hydrogen jets under various conditions.
Conclusions
- The protocol enables the effective operation of cryogenic liquid jets.
- Future studies can extend to different gases and aperture geometries.
- Careful monitoring is essential to prevent system failures.
Frequently Asked Questions
Executive Industry Relevance
Cryogenic liquid jet systems enable high repetition rate target delivery for laser-driven ion acceleration, addressing a critical bottleneck in discovery science platforms. The technology supports mechanistic de-risking in preclinical and translational research by providing reproducible, pure ion beams for probing biological systems under controlled radiation conditions. Its integration into discovery workflows enhances predictive confidence in target validation by allowing high-throughput screening of radiation-induced effects in disease-relevant models.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses through precise ion beam delivery to cellular or tissue models.
- Operational Value: Provides stable, laminar jet output for consistent irradiation parameters across experimental replicates.
Screening & Assay Development
- Scientific Value: Facilitates preparation of validated biological systems for downstream irradiation-based assays.
- Operational Value: Ensures assay standardization through reproducible jet formation and minimal positioning jitter.
Translational & Preclinical Research
- Scientific Value: Supports disease-relevant system evaluation by enabling controlled proton or ion exposure in preclinical models.
- Operational Value: Promotes translational continuity from discovery through preclinical validation via stable, high-repetition-rate target delivery.
Pipeline & Workflow Integration
The method positions within the discovery continuum from hypothesis testing to lead identification, supporting radiation biology studies that inform target validation and mechanistic de-risking.
- Discovery Biology: Enables hypothesis testing and pathway clarification through targeted ion beam application in cellular systems.
- Screening: Delivers assay readiness via highly reproducible jet parameters and low spatial jitter for reliable compound or radiation response evaluation.
- Analytics: Provides quantitative jet stability and laminarity measurements via shadowgraphy to support comparative condition analysis.
- Translational Research: Connects to preclinical continuity by enabling consistent radiation dosing in disease models for risk-adjusted advancement decisions.
- Enterprise Reuse: Represents a reusable platform capability for multiple irradiation-based discovery campaigns rather than a single-use setup.
Operational & Enterprise Impact
- Scientific Value: Predictive confidence in target validation through reduction of mechanistic ambiguity in radiation response studies.
- Operational Value: Standardization, reproducibility, and scalability of ion beam delivery for high-throughput discovery applications.
- Strategic Value: Improved go/no-go decisions, capital efficiency, and reduced late-stage biological risk via early mechanistic insight.
- Portfolio Impact: Risk-adjusted prioritization and advancement decisions based on reproducible radiation effect data.
Implementation Considerations
- Requires expertise in cryogenic systems, fluid dynamics, and laser-plasma interaction principles.
- Depends on precision instrumentation including mass flow controllers, pressure regulators, and high-speed shadowgraphy systems.
- Necessitates cross-team standardization of cleaning, assembly, and environmental control protocols.
- Involves adaptation considerations for different aperture geometries and sample gases beyond hydrogen or deuterium.
- Involves practical limitations including sensitivity to vacuum chamber pressure, gas backing pressure, and temperature fluctuations exceeding ±0.02 K.
