Experiment exposing refractory metals to impacts of 440  GeV/c proton beams for the future design of the CERN antiproton production target: Experiment design and online results

Abstract

The HRMT27-RodTarg experiment employed the HiRadMat facility at CERN to impact intense 440 GeV proton beams onto thin rods 8 mm in diameter, 140 mm in length, and made of high-density materials such as Ir, W, Ta, Mo, and alloys. The purpose of the experiment was to reduce uncertainties on the CERN antiproton target material response and assess the material selection for its future redesign. The experiment was designed to recreate the extreme conditions reached in the production target, estimated in an increase of temperature above 2000°C in less than 0.5 μs and a subsequent compressive-to-tensile pressure wave of several gigapascals. The goals of the experiment were (i) to validate the hydrocode calculations used for the prediction of the antiproton target response and (ii) to identify limits and failure mechanisms of the materials of interest. In order to accomplish these objectives, the experiment relied on extensive instrumentation (pointing at the target rod surfaces). This paper presents a detailed description of the experiment as well as the recorded online results which showed that most of the investigated materials suffered internal damage from conditions 5-7 times below the ones present in the AD target. Tantalum, on the other hand, apparently withstood the most extreme conditions without presenting internal cracking.

Dynamic Response of Graphitic Targets with Tantalum Cores Impacted by Pulsed 440‐GeV Proton Beams

“…Among other refractory metals like molybdenum, tungsten [35], and iridium, tantalum shows the highest resistance towards beam impacts. Even though hydrodynamic simulations and neutron tomography revealed the development of internal cracks induced by high-intensity beam impacts, the dynamic response of tantalum is still quasi-elastic up to the highest beam intensity of ∼1.7 × 10 12 protons for a target diameter of 8 mm [20,34]. Taking the different diameter of 3 mm of the tantalum core of our samples into account, the "limit" for quasi-elastic behaviour of the most loaded tantalum core is estimated to be reached already with ∼9 × 10 11 protons under our experimental conditions.…”

“…All samples of target station 6 (see Figure 1(b)) consist of a 10 mm long tantalum rod of 3 mm diameter press fit into a graphitic cylinder of 10 mm outer diameter (see Figure 2(a)). e geometry of short and bulky targets reduces beam-induced bending modes (with large amplitudes) that superimpose with radial and circumferential vibration modes [20][21][22] and allowed for a compact target station design that could accommodate a large number of different material samples. e fiber-reinforcement plane of all fiber-reinforced targets is oriented normal to the cylinder axis of the samples and thus also normal to the beam axis.…”

Development of a Neutron Imaging Station at the n_TOF Facility of CERN and Applications to Beam Intercepting Devices

“…This leads to a huge and fast energy deposition in the bulk of target material, with its subsequent sudden increase of temperature and appearance of violent stress waves, which can eventually fracture it [15]. This phenomena has been extensively studied both numerically [16] and experimentally [17,18]. For the latter, tests using real proton beams were carried out under the described conditions using CERN's HiRadMat facility [7].…”

“…The HiRadMat-27 experiment was carried out in 2015 in order to obtain, in a controlled environment, analogous conditions to the ones taking place in the AD-Target core [17]. Thirteen targets made of refractory metals, all potential candidates for core materials in a new AD-Target design, were exposed to proton beam impacts in order to crosscheck numerical simulations and assess their response at such conditions.…”

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

“…The Beam Dump Facility conditions require slow extraction of the beam, therefore the HiRadMat facility at CERN [7] could not be used, as done for target technologies tests in the past [8][9][10][11][12][13]. The target prototype experimental setup was therefore located in the North Area target zone of CERN (TCC2), where the SPS proton beam is regularly sent under slow extraction with intensities up to 3-4·10 13 protons per pulse for physics experiments and test beams.…”