# Presentation: 000559

## Progress in Heavy Ion Driven Target Fabrication and Injection ”Mass-production of targets for inertial fusion - the challenge of 500,000 targets/day” D.T. Goodin, A. Nobile, N. B. Alexander, R. Gallix, J.L. Maxwell, R.W. Petzoldt, W. S. Rickman, and E.I. ValmianskiPresented by Dan Goodin

- 15th International Symposium on Heavy Ion Inertial FusionPrinceton Plasma Physics LaboratoryJune 7-11, 2004

## Main points and summary of this talk

**Conclusions:**
**The “pathway” for the HIF target supply is being improved**
**There are several good options for hohlraum materials (tradeoffs!)**
**Estimates of future target mass-fabrication costs are reasonable for energy production**

**Target fabrication is one of the key feasibility issues for inertial fusion energy**
**At HIF2002 we described a “pathway” for fabrication of a high gain, distributed radiator target for energy production**
**Here we provide **_**an update**_** on that pathway with:**
**Streamlining of the steps addressing issues of handling and assembly of the foam materials**
**Preliminary estimates of the per-target cost (in a fusion economy)**
**Evaluation of hohlraum materials and their cost impact**

## The target supply is a feasibility issue for IFE

**Target supply requirements are challenging**
**~500,000/day (6 Hz) precision, cryogenic targets with unique materials**
**Low cost is required for commercial energy production**
**Positioned at center of high-temperature chamber**
**Comparison of laser fusion and heavy ion fusion issues:**
**Direct drive = most difficult issue is injection**
**Indirect drive = most difficult issue is fabrication**

***Heavy Ion Driven HYLIFE-II Plant***

**Cost goals of about $0.25-0.35 per target have been presented**

**Direct drive target heating during injection**

## “Reference” target designs- laser & heavy ion fusion

_**Some Expected Direct Drive Specifications**_
- Capsule Material	CH (DVB) foam
- Capsule Diameter	~4 mm
- Capsule Wall Thickness	290 m
- Foam shell density	20-120 mg/cc
- Out of Round		<1% of radius
- Non-Concentricity	<1% of wall thickness
- Shell Surface Finish	~20 nm RMS
- Ice Surface Finish	<1 m RMS
- Temperature at shot	~15 - 18.5K
- Positioning in chamber	 ± 5 mm
- Alignment with beams	<20 m

_**Some Expected Indirect Drive Specifications**_
- Capsule Material	CH or Be
- Capsule Diameter	~4.6 mm
- Capsule Wall Thickness	250 m
- Out of Round		<1% of radius
- Non-Concentricity	<1% of wall thickness
- Shell Surface Finish	20-200 nm RMS
- Ice Surface Finish	1-10 m RMS
- Temperature	at shot	~15 - 18.5K
- Positioning in chamber	± 1-5 mm
- Alignment with beams	<200 m

***Two sided illumination by heavy ions***
***Unique materials in hohlraum = issue***

**“****Reference” target designs****- laser & heavy ion fusion**

**Direct Drive High Gain Target Design**

***Laser driven***
***Foam shell - divinyl benzene***

*being simplified...*

**Comparison = addition of hohlraum (1) insulates DT during injection, (2) reduces requirements on capsule and (3) on DT “ice” surface finish**

*Callahan and Tabak*

## Overall pathway for HIF target supply has been established

**Pressure cell**

**Micro-**
**encapsulation**

**Major advantages:  started with DP/ICF experience base, synergism with laser fusion and ZFE programs**

**Fabricate Capsules**

**DT Fuel Fill**

**DT Fuel Layer**

**Fabricate hohlraum**

**Load capsule in hohlraum**

**Inject/**
**track**

**Fluidized bed**

**Multiple advanced manufacturing steps**

**Overall pathway for HIF target supply has been established**

**1) Fabricating the spherical capsule**
**2) Filling the capsule with fuel**
**3) Cooling the capsule to cryo**
**4) Layering the DT into shell**
**5) Fabricating the hohlraum case**
**6) Fabricating the radiators**

**  ****6) Assembling the cryo components**
**  ****8) Accelerating for injection**
**  ****9) Tracking the target’s position**
**10) Providing steering/timing info**

**Injector demo experiment**

## Thick walled capsules (HIF, ZFE) & foam capsules (DD) are being made 

**The microencapsulation process has demonstrated the feasibility of fabricating thick-walled and CH overcoated foam capsules - but IFE specifications not yet met**

**Power spectrum of 4.6mm CH capsule, 45 ********m wall, OOR <1% of radius, NC <3% of wall, rate 36/minute (GA)**

- NIF Spec (green)

**Approaching IFE Requirements**

***CH capsule (HIF, ZFE)***

***CH overcoated***
***foam capsule (DD)***

**4 mm dia., 200 ********m foam layer, CH overcoat, production rate - 3 Hz**

**Process Scaleup Studies - HAPL**

## DT filling/layering technologies synergistic with ICF and HAPL

**DT filling/layering technologies synergistic with ICF and HAPL**

**Theoretical minimum DT inventories**

_***HIF Targets***_

**Rapid filling of many capsules (500,000/day)**
**For HIF, issue is acceptable tritium inventory**
**Goal = less than ~1 kg **

**DT Filling - Demonstrated in ICF program**

**Cryogenic fluidized bed layering**

***LANL cooldown data show lower temperatures are possible***

**Proof of principle shown**
**Lab-scale unit being built **

## Improvements in hohlraum concepts

_**Old (HIF2002) hohlraum assembly process**_

**Die set & assemble precast foams (E,D,C)**

**2% W-doped 30 mg/cc CH foam or LCVD **

**Issues = include precise handling and “stacking” of very low-density foams in discrete zones and doing it quickly**

**Continue “stacking” (G,F,H,J,I)**

**Laser-assisted Chemical Vapor Deposition (J. Maxwell, LANL)**

**Epoxy Case**

**Functionally**
**Graded**
**Lattice**

**Capsule**

**Lattice**
**Plug**

**Hohlraum **
**Wall-Coating**

**Thin Film**
**Membranes**

- Laser gives controlled chemical vapor deposition

- Variable Spacing & Fiber DiameterVariable Density

**New proposed process uses LCVD to manufacture most of the hohlraum........**

***Materials range***
***11 - 13,500 mg/cc***

## New hohlraum fabrication concept

**3D-LCVD of Low-p, High-Z Metal Lattices**

**Deposit Hohlraum Exterior Wall**

**Reactive Injection of Polymeric Case**

**Capsule/Plug Insertion and Immediate Target Injection**

**LCVD radiator and assembly process**

**“****Micro-engineered” materials by LCVD**
**- capable of “high-Z only” materials**

**New concept - design for manufacture:**
**Builds from “inside out”**
**Avoids precision machining steps**
**Avoids assembly steps**
**Avoids “split” hohlraum assemblies**
**Auto-aligned final assembly step**
**Maximum use of LCVD process**

**Experimental demonstration is underway........**

## LCVD development is underway

**Close-up of chamber and focusing optics**

**LCVD experimental setup at LANL (PI - James Maxwell)**

- Examples:

**Over 68 Thermodynamic scenarios investigated, to optimize deposition rates**

**WF6 + 3H2 ******** W(s) + 6HF**
**Rapid Growth Expected Above 100C**

**Example fibers**
**~10-15 ********m OD**

## This LCVD process has been incorporated into a plant scaleup/costing study

**Arrays of fibers are essential for mass-production**

**Assume 100x100 spot arrays with 12 micron spacing**
**Axial growth rates ~ 2mm/s (typical now)**
**Each hohlraum takes 12.5 minutes;  Unit Processor grows 48 samples simultaneously; 112 Unit Processors operating in parallel, so 5376 hohlraums made simultaneously.**

**~1500 ft****2**** modular production facility**

## 1)   Production rate ~500,000 targets/day - 1000 MW(e) plant
2)	Pb/Hf (70:30) is high Z material (single use)
Installed capital cost ~ $304M ($38 M annualized cost)
Annual materials and utilities ~$11M
Annual maintenance costs (labor and materials) ~$18M
Annual operating labor costs ~$10 M
Cost per injected target is estimated at ~40.8¢ each
(~32¢ each for 3000 MW(e), ~22¢ each for centralized production)

**2)****	****Pb/Hf (70:30) is high Z material (single use)**
**Installed capital cost ~ $304M ($38 M annualized cost)**
**Annual materials and utilities ~$11M**
**Annual maintenance costs (labor and materials) ~$18M**
**Annual operating labor costs ~$10 M**
**Cost per injected target is estimated at ~40.8¢ each**
***(~32¢ each for 3000 MW(e), ~22¢ each for centralized production)***

***TFF layout for capsule, filling, layering, injection***

***LCVD systems are major capital cost***

**Estimates for indirect drive target production costs**

_**Assumptions**_**:**
**1) R&D programs done**
**2) Major “paradigm shift” from current targets - no first-of-a-kind costs, statistical characterization, increased yield, larger batch sizes**
**3) “nth-of-a-kind” plant, standard engineering cost factors**

## _x0008_Single use versus recycling for hohlraum materials

**...****. single use options results in lower cost of electricity**

**Original basis = recycle hohlraum materials to reduce waste streams**
**Required for Au/Gd design - costs $0.43/target to throw away!**
**But resulting radioactivity results in remote processing/maintenance for target fab**
**Our estimates indicate fully remote makes targets cost more than their E value**
**Single-use:  hohlraum materials make up <1% of total life-cycle plant waste stream**
**Laila El-Guebaly paper Wednesday morning in Fusion Chamber session**
**Other hohlraum materials are much cheaper - but entail an energy penalty**
**Example - replacing Au/Gd with Pb/Hf loses 2% of E but allows single use**
**Pb cost per hohlraum = 0.02 cents (~$100 per day)**
**Hf cost per hohlraum = 1.6 cents (~$8000 per day)**

## Indirect Drive Target Hohlraum Fabrication

**Choosing the right hohlraum material is a key for HIF targets**

**Several material options have been identified for heavy ion driven hohlraums**

| Issue

Mat’l | Target Gain Loss | Target Manufacturing | Separable from Flibe | Waste Hazard | Comment |
| --- | --- | --- | --- | --- | --- |
| Au/Gd | 0 % | High cost |  | Radiation | Must recycle |
| Hg and
Hg/X | 0-13 % | Toxicity | Excellent (Hg) | Mixed Waste | Toxicity prohibitive |
| Pb/Hf
Pb/W | 2 %
4 % | OK ($0.41)
OK | Electrochemical (Hf) | Mixed (Pb) | Pb may attack steel |
| W | 12 % | Excellent | Potential Plating Problem | Low level waste | Once-thru |
| Hg/Hf/Xe/Kr | 0 % | Complex | Electrochemical (Hf), others easy | Mixed Waste | Toxicity prohibitive |

**“****Ref.”**

** ****Cost study**

**LCVD Demo**

**Au/Gd is “reference” with 0% energy loss - recyling drives up cost**
**Hg has advantage of easy removal from molten salt coolant - but toxicity prohibitive**
**Tradeoff - Pb alone loses 14% while Pb/Hf loses only 2% ($150K vs $8K Hf cost)**
**No single element (e.g., W) has less than 12% energy loss = huge cost**
**W is non-toxic - but 12% loss is $150K/day (issue of “attractiveness” for fusion?)**
**Hg/Hf/Xe/Kr has no loss but rather more difficult to produce a target!**

## Summary and conclusions

**Supplying 500,000 targets/day to a 1000 MW(e) power plant will be a challenge**
**A significant target development program is required**
**A target supply pathway has been defined - and recent studies have improved upon its features**
**There are several good  options for hohlraum materials - they all have tradeoffs on costs and attractiveness**
**Estimates of future target mass-fabrication costs are reasonable for energy production**