Application of hot isostatic pressing (HIP) technology to diffusion bond refractory metals for proton beam targets and absorbers at CERN

Abstract

A target assembly, composed of several collinear molybdenum (Mo)‐based and tungsten (W)‐based cylindrical blocks, will reside in the core of the new beam dump facility (BDF) being designed at the European Laboratory for Particle Physics (CERN). The target blocks will be protected from the cooling water erosion‐corrosion by a tantalum (Ta)‐based cladding. In order to obtain intimate and reliable bonding between the several cylinders composing each target block and with the cladding, hot isostatic pressing (HIP) assisted diffusion bonding technique was explored. Several down‐scaled target block prototypes were conceived to investigate the bondings. Starting from the previously gained experience in Ta cladding on W from neutron spallation targets, here, we present results on Ta cladding on TZM (Mo alloy), Ta2.5W (Ta alloy) cladding on TZM and W, and on TZM to TZM and W to W self‐bondings. The resulting interfaces were systematically characterized with electron microscopy, tensile testing, and thermal conductivity measurements. Successful diffusion bonding was achieved for all the studied material combinations, resulting in homogeneous and defect‐free interfaces, strong interfacial bondings, and limited interfacial thermal contact resistance. The HIP parameters and diffusion interfacial aids were of great importance to optimize the interface and bulk material properties.

Beam impact tests of a prototype target for the beam dump facility at CERN: Experimental setup and preliminary analysis of the online results

“…At the design stage of the target prototype, a good mechanical and chemical bonding between tungsten and Ta2.5W had not been produced via the HIP process. A successful bonding was later on achieved by adapting the HIP parameters employed [19], validating the use of Ta2.5W as cladding material for all the target blocks in the final BDF target.…”

“…The use of Ta2.5W as cladding material is novel for a production target, while pure tantalum has already proven to be a reliable cladding material for tungsten blocks in other facilities (LANSCE, KENS and ISIS neutron source) [16][17][18]. Therefore, in the BDF target prototype both pure tantalum and Ta2.5W were used as cladding materials to compare their performance under beam irradiation [19].…”

“…The core and cladding materials were joined via diffusion bonding achieved by means of Hot Isostatic Pressing (HIP), using a manufacturing process identical to the one of the final target blocks [5,19]. A summary of the ma- View of the refractory metal parts required for the production of a Ta2.5W-clad TZM target block (80 mm diameter, 25 mm length) for the BDF target prototype.…”

Design of the third-generation neutron spallation target for the CERN’s n_TOF facility

“…The excellent corrosion resistance of tantalum would solve the contamination issues, while the better thermo-mechanical properties of tungsten and tantalum (compared to lead) would eliminate any thermo-structural concern even for higher average power on target. Moreover, the HIP process would provide an excellent thermal conductance at the Ta-W interface and a lot of experience had already been acquired at CERN on R&D of HIPed Ta-W assemblies [8]. For the external tungsten mass, a gas circuit or even natural convection would suffice for an adequate cooling.…”

Development and Beam Irradiation of Ir/W/Ta/Ta-Alloys Refractory Metals and Cladding Via Hot Isostatic Pressing at CERN for Beam Intercepting Devices Applications

“…Details about the process are reported extensively in Ref. [12] together with the relevant references.…”