# Presentation: 125100

## High Power Target Material R&D	

**N. Simos, BNL**

- NFMCC Meeting, UCLA, CA

## 4 MW proton driver? Operational Envelope & Inter-dependency of KEY parameters 

**4 MW proton driver? ****Operational Envelope & Inter-dependency of KEY parameters**

**Desired bunch length  **
**as low as 2 ns  !!!**

- NFMCC Meeting, UCLA, CA

## Solid Targets – How far can they go?

| 1 MW ?

Answer is YES for several materials

Irradiation damage is of primary concern

Material irradiation R&D pushing ever closer to anticipated atomic displacements while considering new alloys are needed | 4 MW ?
Answer dependant on 2 key parameters:
1 – rep rate
2 -  beam size compliant with the  physics sought

A1: for rep-rate > 50 Hz + spot > 2mm RMS  4 MW possible (see note below)

A2: for rep-rate < 50 Hz + spot < 2mm RMS
 Not feasible (ONLY moving targets)

NOTE: While thermo-mechanical shock may be manageable, removing heat from target at 4 MW might prove to be the challenge. 
CAN only be validated with experiments |
| --- | --- |

- NFMCC Meeting, UCLA, CA

## R&D on irradiation damage

- What does it mean for materials (microscopic & macroscopic terms) ?generation of voids/dislocations	 changes in physical and mechanical propertiestrapping of gases, swelling	 density reduction

- Effects of neutron irradiation from reactor experience**Question: does radiation type matter?**

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## Experimental Process Utilizing BNL Accelerator Complex

- Experimental Process Utilizing BNL Accelerator Complex

- Post irradiation analysis at
- BNL Hot Labs

**Thermal Expansion/Heat Capacity Measuring System**

**Remotely operated mechanical **
**testing system**

**BEAM on Targets**

- Irradiation takes place at BLIP
- using 200 MeV or 117 MeV protons at the end of Linac

**Bldg 801**

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## IRRADIATION STUDIES

_**PHASE I**_**:**
**Super Invar and Inconel-718**

**  ****3D Carbon-Carbon Composite **
**   ****Toyota “Gum Metal”**
**   ****Graphite (IG-43) **
**   ****AlBeMet **
**   ****Beryllium **
**   ****Ti Alloy (6Al-4V) **
**   ****Vascomax **
**   ****Nickel-Plated Alum. **

**BEAM**

_**PHASE II**_**:**

_**PHASE II-a**_**:**
**2D Carbon-Carbon**

_**PHASE III**_**:**

**  ****3D & 2D Carbon-Carbon**
**   ****90% cold-worked “Gum Metal”**
**   ****Graphite (IG-43 & IG-430) **
**   ****AlBeMet **
**   ****Ti Alloy (6Al-4V) **
**  ****Copper & Glidcop**
**  ****W and Ta**
**   ****Vascomax **
**   ****Nickel-Plated Aluminum**
**  ****Super-Invar ******** ****following annealing**
** ****Graphite/titanium bonded target**

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##  PHASE III - Preparations 

** ****PHASE III - Preparations **

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## Specially bonded graphite/titanium target exposed to proton irradiation 

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##  Graphite vs. Carbon-Carbon 

** ****Graphite vs. Carbon-Carbon**** **

**3D CC**

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## 3D CC Annealing Behavior !!

- Good news were associated with modest beam exposure (~ 25,000 uA-hrs). More needed to be done to validate that carbon composites can replace graphite.

- Radiation changes material
- dramatically

- Thermal cycling
- restores it

- 45-degree plane (“weak” orientation)

- 90-degree fiber orientation

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##  Embarked into a 2-phase new study

Phase 1 	Assess the 2D carbon-carbon under heavy 			irradiation

Phase 2 	Expose 2D & 3D carbon-carbon composites 			under identical experimental conditions

- Phase 1 	Assess the 2D carbon-carbon under heavy 			irradiation
- Phase 2 	Expose 2D & 3D carbon-carbon composites 			under identical experimental conditions

- NFMCC Meeting, UCLA, CA

## Phase-1: 2D Carbon Composite

- PEAK integrated flux achieved  **~ 7 x 10^21 protons/cm^2**
- 	Integrated beam current ~ 108,000 uA-hrs
- Post-irradiation analysis of the exposed 2-D carbon composite revealed both good and bad news:
- 	GOOD NEWS:	the composite exhibits self-healing behavior
- 			(as in the case of the 3-D counterpart)
- 	BAD NEWS:	Serious structural degradation is observed as a result of high fluences
- 			Damage more pronounced along the “weak” orientation

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## Good News: 2D carbon composite exhibits self-healing through thermal annealing

- “strong” orientation

- Compare with 3D counterpart

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## How well is our nanometer-level analysis controlled/stabilized? 

- 2.70 mCi

- 7.62 mCi

- 8.08 mCi

- 4.62 mCi

- COMPARE !

- NFMCC Meeting, UCLA, CA

## Bad News: Structural degradation

- “weak” orientation

- “strong” orientation

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##  
“Unexpected” 2-D CC damage left us scratching our heads 

Is it just the 2D carbon composite that is susceptible to high fluences 
OR
This holds true will ALL carbon composites (2D & 3D) ?

_**“**__**Unexpected” 2-D CC damage left us scratching our heads **_
- Is it just the 2D carbon composite that is susceptible to high fluences
- OR
- This holds true will ALL carbon composites (2D & 3D) ?

** ****The mixed-bag of news prompted us to go through another exposure where 2D and 3D carbon composites are irradiated under identical conditions**
- Irradiation of the two carbon composites along with two graphite grades (IG-43 and IG-430) was performed in Spring 2006. Integrated current reached ~ 50,000 uA-hrs (but likely under tighter beam spot!!)

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## PRELIMINARY assessment of exposures

- 2005 Irradiation

- 2006 Irradiation

- Nickel foils of the 2006 irradiation are currently being analyzed (radiography)
- to establish shape of proton beam

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## Damage in 3-D carbon composite. Note the complete disintegration of irradiated specimens situated within the 1-sigma of the beam

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## Damage even worse in 2-D carbon composite. 
Severe disintegration especially of “weak-orientation” falling within 1-sigma of the beam

**Severe disintegration especially of “weak-orientation” falling within 1-sigma of the beam**

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## BACK TO THE DRAWING BOARD 

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## Take another look at super-InvarLook into other super-alloys (gum metal, titanium alloys, etc.)Explore new graphite gradesFurther evaluate AlBeMetRe-assess high-Z range (Ta, W)

- NFMCC Meeting, UCLA, CA

## Re-evaluation of super Invar

**Modest level of irradiation takes away the low thermal expansion exhibited by the un-irradiated super Invar **

**Thermal cycling with temp. threshold identified experimentally as ****T*****threshold *****> 600 C**
**restores material !!**

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## Re-evaluation of super Invar

- Remote RE-ASSEMBLY in Hot Cell
- Half of layer undergone annealing (>600 C)

- Back in the “OVEN” !!!

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## Slide 24

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## Slide 25

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## Questions to be answered regarding annealing

- How is irradiation damage influenced by high temperatures during irradiation and if yes where is the threshold?
- A difficult but not impossible task – achieve same exposure at different irradiation temperatures
- Identifying the temperature threshold will allow for life extension of the material in the irradiation environment
- Do materials exhibit similar damage following annealing and re-irradiation ?
- Studies from neutron exposure indicate that the number of voids, while decrease in size, increase in number during re-irradiation
- To address that, irradiated and then annealed super-Invar has been exposed to irradiation

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## Radiation effect on ductility & strength – How important is ductility?

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## The high expectations of gum metal

**The high expectations of gum metal**

**Super ductility completely **
**disappears with irradiation**

**2****nd**** Cycle**

**1st Cycle**

- Enhancement of properties are attributed to the “dislocation-free” plastic deformation mechanism

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## Serious degradation of magnetic horn material 

- Serious degradation of magnetic horn material
- (nickel-plated aluminum) used in the NuMI experiment at FNAL!
- Retested during Phase III with double the exposure and waiting examination

**After irradiation**

**Before irradiation**

- NFMCC Meeting, UCLA, CA

## SUMMARY

- The value of performing R&D prior to moving too far ahead based on “expectations” has been clearly demonstrated
- Further experimental scrutiny of 2D or 3D carbon composites for irradiation damage effects is not recommended. These composites clearly CANNOT tolerate the high fluences required by high-power beam targets. These results should prompt a change of course in the search for materials for the multi-MW beam targets.
- FOCUS needs to be shifted toward:
- Low-Z: new graphite grades such as isotropic graphite IG-430 and AlBeMet
- Mid-Z: Titanium alloys, Vascomax, super-Invar
- High-Z: New alloys of Ta and W

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## Some interesting irradiation damage findings !!! 

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## Ceramics/Resistors/Capacitors integrated with quartz rods and CZT crystals

- CZT Crystals

- Resistors

- Capacitors

- Ceramic
- TYPE A

- Ceramic
- TYPE B

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## Neutron Exposure 

**Neutron Exposure **

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##  Crystal (SO2) before irradiation

** ****Crystal (SO2) before irradiation**

** ****Crystal (SO2) AFTER irradiation**

** ****Crystal (SO2) AFTER irradiation**

- NFMCC Meeting, UCLA, CA