Constitutive Models for the Viscoelastic Behavior of Polyimide Membranes at Room and Deep Cryogenic Temperatures

Journal Article · Thu Jun 30 00:00:00 EDT 2016 · Fusion Science and Technology

DOI:https://doi.org/10.13182/FST15-218· OSTI ID:1343043

Bhandarkar, Suhas ^[1]; Betcher, Jacob ^[2]; Smith, Ryan ^[2]; Lairson, Bruce ^[2]; Ayers, Travis ^[2]

---

1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Luxel Corp., Friday Harbor, WA (United States)

Targets for ICF shots on NIF typically use ~500nm thin polyimide films with a coating of 25nm of aluminum as windows that seal the laser entrance hole or LEH. Their role is to contain the hohlraum gas and minimize the extraneous infra-red radiation getting in. This is necessary to precisely control the hohlraum thermal environment for layering inside the capsule with solid deuterium-tritium at 18K. Here, we use our empirical data on the bulging behavior of these foils under various different conditions to develop models to capture the complex viscoelastic behavior of these films at both ambient and cryogenic temperatures. The constitutive equations derived from these models give us the ability to quantitatively specify the film’s behavior during the fielding of these targets and set the best parameters for new target designs.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1343043
• Report Number(s): LLNL-JRNL-677537; TRN: US1701814
• Journal Information: Fusion Science and Technology, Vol. 70, Issue 2; ISSN 1536-1055
• Publisher: American Nuclear Society
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING