T2K Neutrino Experiment
29 Mar 2018




We have designed and supplied crucial components that generate the neutrino beam for the international T2K experiment in Japan




Log of the T2K Experiment; click to go to the T2K website​​The T2K​ experiment began in 2008. It sends the world’s most intense neutrino beam from the JPARC facility at Tokai in the east of Japan 295 km through the earth to the Super Kamiokande neutrino dete​ctor in the west of the country, with the aim of studying the properties of these tiny, weakly interacting particles.

​We are responsible for the

3D CAD of the target assembly.  In the centre is a long, thin graphite rod, in a longer, close-fitting tube, surrounded by a wider tube for coolant, all projecting from the necessary pupework etc to supprt it. 

Cross-section of the T2K target installed in magnetic horn


Neutrino Production Target​

We are responsible for the T2K neutrino production target which converts the high power proton beam into neutrinos. It is a 1 metre long graphite rod encased in a titanium container cooled with helium. We designed and optimised the target for mechanical and thermal stresses using ANSYS Finite Element Analysis (FEA) code and the flow using ANSYS CFX Computational Fluid Dynamics (CFD). The target is designed to cope with a proton beam power of 750kW and work is currently underway to upgrade it so the power can be increased to 1.3MW.​​

A photograph of a T2K target rod and connecting pipework. The rod is mounted on a carrying platform which can move along a rail. Two robot arms are pushing the platform along the rail. The target is about to be inserted into a large circular flange surrounded by bolts. The rail is helping the robot arms to keep the target and flange accurately aligned. 

T2K Target remote exchanger system


Target exchange mechanism

​ We designed and developed a remote exchange system which permits highly radioactive failed targets to be safely and quickly replaced using master-slave manipulators in a remote maintenance area. This allows the large and expensive magnetic horn in which the target is installed to be reused saving money and reducing radioactive waste. This is a challenging task as the clearance between the target and horn bore is only 3mm and the target is 1 metre long and contains delicate graphite components.​
Rectangular assembly suspended at  the top, with an engineer adjusting one of the fittings. The assembly consists of two solid metal plates back to back, which are the bellows.  In the centre is a stubby tube, within which the hemispherical window is surrounded by mirror-finish metal plates (there is an identical dome on the other side). TWo tubes protrude from the top.   

T2K window assembly. In the centre of the assembly a hemispherical structure can be seen which is the thin titanium beam window. Around the window is the inflatable metal seal which consists of a two mirror polished foils connected to metal bellows.


​Vacuum-to-air beam window​

The T2K beam window separates the accelerator vacuum from the target station helium volume at atmospheric pressure. The window consists of two thin partially spherical domes of titanium alloy cooled by helium to remove the heat generated by the passage of the proton beam. It is remotely replaceable and seals to mirror flanges using inflatable metal seals.​ ​

Image of helium streamlines in the T2K beam window from a Computational Fluid Dynamics simulation. The streamlines are coloured according to the velocity of helium flow. The dominant helium flow is across the centre of the window with large areas of recirculation to the sides. The highest velocity and localised turbulence is located in the helium outlet channel. 

A Computational Fluid Dynamics (CFD) plot showing helium streamlines between the titanium domes.


On the left is a photo of an engineer assembling the T2K collimator/baffle. The zinc plated steel cladding of the baffle appears as a long rectangular box; the graphite core can be seen through a circular hole at the end..  The approximate size of the baffle is 30cm by 40cm by 170cm. On the right is a Computer Aided Design (CAD) image of the T2K collimator/baffle. The main assembly is suspended by shafts at each corner from an adjustable rectangular frame. At the front end of the photo the water cooling pipes are shown. 

The T2K collimator/baffle : [Left] The graphite core can be seen where the engineer is making an adjustment. [Right] CAD design of the T2K collimator/baffle



The T2K baffle/collimator is situated between the beam window and target. The main functions of the this component are:

  1. To protect the target, magnetic horns and hadron absorber from damage due to a mis-steered proton beam;
  2. To reduce activation and damage of components upstream of the target.

The core of the baffle consists of a large block graphite. The graphite block has a 30mm bore for the proton beam to pass through under normal conditions. To protect the graphite and reduce future radiological contamination the graphite is clad in zinc coated steel plates. The baffle incorporates thick steel shielding blocks which fit into the target station shielding to create a labyrinth seal and reduce radiation backscattering from the target to the final focusing section magnets. To keep the assembly cool during operation it has cooling pipes embedded in the outer edges of the graphite.

On the left, the plot of the hadron absorber is coloured to show deflections due to thermal expansion. The maximum defections are coloured red and located in the centre of the absorber at the front. The minimum deflections are at the back of the absorber and coloured blue. On the right, an engineer in protective clothing and a hard hat is in front of a stack of black blocks, each around a metre long and half a metre high and deep.  The stack is two wide (lengthways), 7 high and 7 deep.  ​​

The Hadron Absorber. [Left] Finite Element Analysis (FEA) plot of the hadron absorber assembly showing deflections due to thermal expansion. [Right] Engineer standing in front of the hadron absorber during construction. The hadron absorber consists of segmental graphite blocks with cooler modules on the sides. The size of the assembly is 2.3 metres wide and 4.7 metres tall.


Hadron absorber​

The hadron absorber is a large assembly of graphite blocks that must absorb the remnant hadrons some 100 metres downstream of the production target. It is cooled by aluminium cooling modules connected to the ends of the graphite block. The hadron absorber is not replaceable or upgradable so it has been designed to cope with 3MW beam power.​​

Contact: High Power Targets Group
Chris Densham
Tel: 01235 446273​​