1. Tungsten Powder Test at HiRadMat Scientific Motivation
P. Loveridge, T. Davenne, O. Caretta, C. Densham, J. O’Dell, N. Charitonidis
23 April 2011

2. Motivation
Designing targets for new accelerator based facilities is becoming more and more challenging due to increasing accelerator beam power and the associated power deposition in the target.
Targets must sometimes accommodate significant power deposition in continuous form or sometimes as an intense pulse followed by an interval of cooling.
Maintaining the target temperature and stress levels within safe limits is the main design driver and results in increasingly elaborate designs as time averaged and pulse power deposition are increased
Solid peripherally
cooled targets Segmented Targets
Flowing or rotating
Targets
Increasing Power Deposition

3. Solid targets Helium cooling Titanium target body
~940 mm
Titanium target body
Graphite (ToyoTanso IG-43)
Helium cooling
Graphite to titanium diffusion bond
Ti-6Al-4V tube and windows (0.3 mm thick)
T2K target designed for
750kW beam
Prefer small diameter to conduct heat to surface
Limit of approximately 1MW for peripherally cooled solid targets
Prefer large beam sigma to reduce dynamic stress due to pulsed beam

4. Segmented targets ISIS Euronu superbeam Packed bed Concept for
4MW beam
Increased surface area. Coolant reaching
maximum energy deposition region. Reduced static and dynamic stresses.
Increased beam power possible with thinner plates

5. Flowing and rotating targets
SNS mercury target
Continuously refresh target material to accommodate multi-MW power deposition
Gap of 2mm
5MW ESS target wheel concept

6. Limitations of target technologies
Flowing or rotating targets
Segmented
Peripherally cooled monolith

7. Thermal Shock in liquid targets
Merit, Flowing mercury jet 14GeV proton beam Kirk et al.
Pulsed proton irradiation of mercury target. Cavitation of mecury causing damage to annealed stainless steel containment
LANSCE-WNR
Riemer et al.

8. Is there a ‘missing link’ target technology?
Open jets
SOLIDS
LIQUIDS
Monolithic
Flowing powder
Contained liquids
Segmented
Some potential advantages of a flowing powder:
Resistant to shock waves
Quasi-liquid: can be conveyed in a pipe
Offline cooling
Few moving parts
Mature technology
Areas of concern can be tested off-line

9. Potential Multi-MW Powder Target Applications
Open jet:
Contained discontinuous dense phase:
Powder target integrated with magnetic horn for superbeam
Contained continuous dense phase:
Powder target integrated with solenoid for Neutrino factory

10. Tungsten Powder Test Programme1 2 3 4
1. Suction / Lift
2. Load Hopper
3. Pressurise Hopper
4. Powder Ejection and Observation
Plant at RAL developed to do offline testing
Dense phase and lean phase transport
Erosion studies
Heat transfer and cooling of powder
Low Velocity
High Velocity

11. Motivation for in-beam powder test
Splash and cavitation in a liquid (mercury) is a result of propagation and reflection of pressure waves through a continuous medium.
It has been asserted that powder will not be subject to splashing or violent events because of its discrete nature. Individual powder grains do not easily transmit pressure waves to neighbouring grains and as such pressure waves tend to be contained within the grains.
A mechanism for a powder eruption has been identified as a result of a beam induced pressure rise in the carrier gas. The expansion of the carrier gas may be violent enough to aerodynamically lift some powder. While this is a potentially interesting threshold to find we expect that it will confirm that eruption velocities are small compare to the splashing velocities observed with mercury.
In order to confirm these assertions the response of a powder target to the proton beam must be tested to definitively answer the following two questions
Will a powder target splash/erupt?
Can you propagate a pressure wave through a powder target to its container?

12. Mercury Thimble In-beam test