Ultra-thin polymer foil cryogenic window for antiproton deceleration and storage

Area of Science:

• Materials Science
• Particle Physics
• Cryogenics

Background:

• Cryogenic windows are crucial for experiments requiring low temperatures and vacuum.
• Existing windows face challenges with pressure differentials, leak rates, and particle transparency.
• Efficient antiproton beam transfer necessitates specialized window materials.

Purpose of the Study:

• To design and characterize a novel cryogenic window for particle transmission.
• To optimize the window's properties for antiproton deceleration and transfer.
• To ensure the window's mechanical and thermal stability under experimental conditions.

Main Methods:

• Fabrication of ultra-thin (∼1.7 μm) aluminized biaxially oriented polyethylene terephthalate foil windows.
• Testing of various aluminum coating thicknesses (900–2160 nm) for antiproton energy degradation.
• Performance evaluation under pressure differences (>1 bar) and low leak rates (<1×10⁻⁹ mbar l/s) at T < 10 K.
• Comprehensive thermal, mechanical, and permeation tests.

Main Results:

• The cryogenic window withstands >1 bar pressure difference with <1×10⁻⁹ mbar l/s leak rate at T < 10 K.
• A 1760 nm aluminum coating optimally decelerates 100 keV antiprotons to 5 keV.
• The final design, with seven 1 mm holes, transmits up to 2.5% of the injected antiproton beam.
• Permeation and mechanical tests confirmed window robustness.

Conclusions:

• The developed ultra-thin cryogenic window meets stringent requirements for low-temperature particle experiments.
• It enables efficient antiproton beam transfer with minimal energy loss and high vacuum integrity.
• This technology is suitable for particle physics facilities like CERN's Antiproton Decelerator.