Platform Purpose
The implosion platforms used on the National Ignition Facility serve several purposes.
- "Symmetry Capsules" or "SymCaps" (figure 2 below) are imploded inside laser-heated hohlraums. These are almost identical to ignition capsules except they do not contain a fuel layer but rather a hydrogen-helium gas mixture and serve as a surrogate to measure the shape of the implosion by imaging the X-ray flash emitted by the central hot spot plasma at stagnation. Because these are driven by a shaped laser pulse designed to keep the target on a low adiabat, they generate relatively cool, ~2–4 keV, relatively dense, ~20–40 g/cc, hot spot plasmas.
- THD capsules are imploded inside laser-driven hohlraums and are designed to study and optimize the hydrodynamic assembly of the fuel without α-heating in a diagnostics-rich environment. They contain solid cryogenic fuel layers that are hydrodynamically equivalent to DT layers and have a composition of ~74% tritium (T), 24% hydrogen (H), and ~2% deuterium. The neutron yield is around 1014, which allows both neutron and X-ray diagnostics to work. The shaped laser pulse that keeps most of the fuel nearly Fermi degenerate results in very high densities in the main fuel, ~1000 g/cc, which surrounds a lower-density (~100 g/cc) hot spot with a temperature ~4 keV.
- DT ignition capsules (figure 1 below) are imploded inside laser-driven hohlraums and are designed to ignite and burn producing ~10–20 MJ of energy. They contain solid cryogenic DT fuel layers. The laser pulse and target parameters must first be fine tuned precisely in a series of experiments before ignition can be expected. The neutron yield in these experiments can be expected to be in the range of ~1017– 1019 depending on the design. The burn is extremely rapid, lasting ~20 ps. Burn average temperatures and densities can be expected to be in the range of ~30 keV and ~1000 g/cc respectively.
- Exploding pushers are directly driven targets that produce high-temperature, ~10 keV, relatively low-density (~5 g/cc) environments. The specific conditions depend on the design. Their main function in the NIC is to provide sources of 14-MeV neutrons for diagnostics commissioning. Targets typically consist of thin-walled glass spheres ~2 mm in diameter, filled with DT gas, although other gases can be readily added.
Laser and Target Configuration
The laser and target configurations for this platform are summarized below:
Target | # beams | Laser energy/Pulse width |
---|---|---|
CH capsule with cryogenic THD layer | 192 | 1–1.5 MJ ignition pulse |
CH capsule with cryogenic DT layer | 192 | 1.5 MJ ignition pulse |
CH SymCap with H:He gas fill | 192 | 0.3–1 MJ 2-ns Gaussian |
Glass capsule with DT fill | 192 | 0.3–1MJ 2-ns Gaussian |
Diagnostic Configuration
There are a large number of diagnostics planned to measure neutron, X-ray, and γ-ray emission from these implosions.
Diagnostic Name | Acronym | Purpose |
---|---|---|
Neutron Time of Flight- 4.5m | NTOF(2) | Neutron time of flight measurement - 4.5 meter |
Neutron Time of Flight- 20m | NTOF(20) | Neutron time of flight measurement - 20 meter (2 detectors) |
Gamma Ray History- 1 | GRH1 | Time and spectrally resolved gamma emission |
Radiation Chemistry | Rad Chem1 | Neutron activation, gaseous collection |
Radiation Chemistry | Rad Chem2 | Charged particle activation, solid collection |
Advanced Radiographic Capability | ARC | High energy, short pulse backlighter - 2 views (additional views planned to be available) |
Magnetic Recoil Spectrometer | MRS | Neutron spectrum- neutrons converted to protons, energy analyzed by magnetic deflection |
Hardened X-ray Streak Camera | hSXD | Hardened time streaked x-ray camera |
High Energy X-ray Imager | HEXRI | High energy x-ray imaging system |
Hardened High Energy X-ray Imager | HEXRI SE | Hardened version of HEXRI |
Neutron Wedge Range Filter Spectrometer | WRF | Energy resolved particle emission- neutron yield and spectral shape, EMP insensitive |
Neutron Imager | NI | Image primary and downscattered neutrons |
Proton Emission | Protex | Analysis of emitted protons |
Neutron Activation Detector | NAD | Absolute broadband neutron spectrometer by activation of witness foils |
For further information on scientific opportunities at the NIF, please contact:
User Office
PHONE: (925) 422-2179
nifuseroffice [at] llnl.gov (nifuseroffice[at]llnl[dot]gov)