Silica Final Lenses under HIPER Laser Fusion Reactor Operation...
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Experimental facility HiPER 4a (operation in bunch mode for scientific viability) [3] Neutron Flux γ-rays Dose Thermal annealing Silica Final Lenses under HIPER Laser Fusion Reactor Operation Conditions REFERENCES: [1] G. Zimmerman et al., Journal of the Optical Society of America 68 (1975) 549. [2] J. Perkins. Internal report (http://www.docstoc.com/docs/54806737/Temperature- Response-and-Ion-Deposition-in-the-1-mm) [3] Proc. of SPIE Vol. 7916 79160S [4] Marshal et al., Journal of Non-Crystalline Solids 212 (1997) 59-73. The authors thank the Spanish Ministry of Science and Innovation for economical support via the ACI-PROMOCIA program 2009. Finite element solver ASTER CODE is used to estimate temperature, stresses and deformation in final lenses. Ions must be mitigated to avoid melting. X-rays are tolerable, they lead to maximum compression stresses of 0.65 MPa, corresponding to maximum temperature increase below 15 K in one shot. Neutrons and γ-rays lead to negligible thermo- mechanical effects in bunch mode. ODC and E’ defects increase with each pulse due to neutron and γ-ray irradiation, producing laser absorption at λ=350 nm. Even at RT absorption remains below 5% in the lifetime of HiPER 4a (<6000 shots). Anyway thermal annealing (see inset) restores lens transparency. Demo Power Plant HiPER 4b (operation in continuous mode for commercial demonstration) Geometry Thermo-mechanical response Absorption by colour centres [4] Introduction We have studied the thermo-mechanical response and atomistic degradation of final lenses in HiPER project. Final silica lenses are squares of 75 × 75 cm 2 with a thickness of 5 cm. There are two scenarios where lenses are located at 8 m from the centre: •HiPER 4a, bunches of 100 shots (maximum 5 DT shots <48 MJ at ≈0.1 Hz). No blanket in chamber geometry. •HiPER 4b, continuous mode with shots ≈50 MJ at 10 Hz to generate 0.5 GW. Liquid metal blanket in chamber design. Irradiation conditions From the spectra of a 48 MJ shock ignition target from LASNEX [1,2], we have calculated based on our reactor designs realistic: neutron and γ-ray doses with MCNPX; ion energy deposition with SRIM; and X-ray energy deposition with appropriate absorption coefficients. Ion and X-ray deposit most of their energy density in the first 10 μm. The reactor chamber is a spherical steel chamber of 5 m inner radius with 10 cm thickness and 1 mm W armor. 48 laser beam lines are used for symmetrical illumination of direct targets. Final silica transmission lenses are located at 8m from the chamber centre. Final lens dimensions are 75 × 75 × 5 cm 3 . Radiation shielding are showed in the figure above. Absorption by colour centres Thermo-mechanical response Geometry Conclusions •Silica lenses withstand irradiation conditions of HiPER 4a. Colour centre generation leads to higher absorption, however, the lens lifetime exceeds HiPER 4a operation time. •Thermal gradients appear inside the lenses under HiPER 4b conditions with detrimental effects such as aberrations, focal length change and operation complexity. In continuous mode the role of neutrons and γ-rays are of paramount importance. 3D finite element calculations show that a steady state situation is reached very fast (≈25000 shots equivalent to ≈40 min at 10 Hz). It is remarkable the appearance of a thermal gradient along both the axial and radial directions of the lens. The consequence is a varying refractive index. In addition note, that side facing the target reaches higher temperature than the back side due to direct exposure to X-rays. As in the previous case ions must be mitigated. The associated stress do not induce deleterious effects in any case. For the power plant concept we have developed a chamber of 6.5 m inner radius provided with a metal liquid blanket (thickness 1m). Final silica transmission lenses are located at 8m from the chamber centre, as in the previous case. Final lens dimensions are 75 × 75 × 5 cm 3 . Realistic radiation fluxes have been calculated making use of this geometry. In steady state the lens temperature is higher that 800 K, therefore defect annealing is very efficient resulting in low optical absorption. Summary •The reactor start up procedure is conditioned by change in refractive index until steady state is reached (focal length may vary up to 10 cm). •The temperature gradient leads to differences in refractive index inside the lens possible origin of aberrations. D. Garoz, A. Rivera, R. Juarez*, J. Alvarez , R. Gonzalez-Arrabal, J. M. Perlado Instituto Fusión Nuclear (DENIM) - Universidad Politécnica Madrid *Departamento de Ingeniería Energética - UNED
Transcript of Silica Final Lenses under HIPER Laser Fusion Reactor Operation...
Experimental facility HiPER 4a (operation in bunch mode for scientific viability) [3]
Neutron Flux γ-rays Dose
Thermal annealing
Silica Final Lenses under HIPER Laser Fusion Reactor Operation Conditions
REFERENCES:
[1] G. Zimmerman et al., Journal of the Optical Society of America 68 (1975) 549.
[2] J. Perkins. Internal report (http://www.docstoc.com/docs/54806737/Temperature-
Response-and-Ion-Deposition-in-the-1-mm)
[3] Proc. of SPIE Vol. 7916 79160S
[4] Marshal et al., Journal of Non-Crystalline Solids 212 (1997) 59-73.
The authors thank the Spanish Ministry of Science and Innovation for economical
support via the ACI-PROMOCIA program 2009.
Finite element solver ASTER CODE isused to estimate temperature, stressesand deformation in final lenses.
Ions must be mitigated to avoidmelting. X-rays are tolerable, theylead to maximum compressionstresses of 0.65 MPa, correspondingto maximum temperature increasebelow 15 K in one shot. Neutrons andγ-rays lead to negligible thermo-mechanical effects in bunch mode.
ODC and E’ defects increase witheach pulse due to neutron andγ-ray irradiation, producing laser
absorption at λ=350 nm.
Even at RT absorptionremains below 5% in thelifetime of HiPER 4a (<6000shots). Anyway thermalannealing (see inset)restores lens transparency.
Demo Power Plant HiPER 4b (operation in continuous mode for commercial demonstration)
Geometry Thermo-mechanical response Absorption by colour centres [4]
Introduction
We have studied the thermo-mechanical response and atomisticdegradation of final lenses in HiPER project. Final silica lensesare squares of 75 × 75 cm2 with a thickness of 5 cm. There aretwo scenarios where lenses are located at 8 m from the centre:•HiPER 4a, bunches of 100 shots (maximum 5 DT shots <48 MJ at≈0.1 Hz). No blanket in chamber geometry.•HiPER 4b, continuous mode with shots ≈50 MJ at 10 Hz togenerate 0.5 GW. Liquid metal blanket in chamber design.
Irradiation conditions From the spectra of a 48 MJ shockignition target from LASNEX [1,2], wehave calculated based on our reactordesigns realistic: neutron and γ-raydoses with MCNPX; ion energydeposition with SRIM; and X-rayenergy deposition with appropriateabsorption coefficients. Ion and X-raydeposit most of their energy densityin the first 10 μm.
The reactor chamber is a sphericalsteel chamber of 5 m inner radius with10 cm thickness and 1 mm W armor.48 laser beam lines are used forsymmetrical illumination of directtargets. Final silica transmission lensesare located at 8 m from the chambercentre. Final lens dimensions are 75 ×75 × 5 cm3. Radiation shielding areshowed in the figure above.
Absorption by colour centresThermo-mechanical responseGeometry
Conclusions•Silica lenses withstand irradiation conditions of HiPER 4a. Colour centre generation leads to higher absorption, however, the lens lifetime exceeds HiPER 4a operation time.•Thermal gradients appear inside the lenses under HiPER 4b conditions with detrimental effects such as aberrations, focal length change and operation complexity.
In continuous mode the role of neutrons and γ-rays are ofparamount importance. 3D finite element calculations show that asteady state situation is reached very fast (≈25000 shots equivalent to≈40 min at 10 Hz).
It is remarkable theappearance of a thermalgradient along both the axialand radial directions of thelens. The consequence is avarying refractive index. Inaddition note, that side facingthe target reaches highertemperature than the backside due to direct exposureto X-rays. As in the previouscase ions must be mitigated.The associated stress do notinduce deleterious effects inany case.
For the power plant concept wehave developed a chamber of 6.5m inner radius provided with ametal liquid blanket (thickness1m). Final silica transmissionlenses are located at 8 m from thechamber centre, as in theprevious case. Final lensdimensions are 75 × 75 × 5 cm3.Realistic radiation fluxes havebeen calculated making use ofthis geometry.
In steady state the lens temperatureis higher that 800 K, therefore defectannealing is very efficient resulting inlow optical absorption.
Summary•The reactor start up procedure isconditioned by change in refractiveindex until steady state is reached (focallength may vary up to 10 cm).•The temperature gradient leads todifferences in refractive index inside thelens possible origin of aberrations.
D. Garoz, A. Rivera, R. Juarez*, J. Alvarez , R. Gonzalez-Arrabal, J. M. Perlado Instituto Fusión Nuclear (DENIM) - Universidad Politécnica Madrid
*Departamento de Ingeniería Energética - UNED
