A brief history of

the JET project

man

Height 13 m

AcknowledgementsJET was designed by a team led by P. H. Rebut

R. J. Bickerton, scientific director, encouraged many UKAEA Culham based scientists (including myself) to join the JET Joint Undertaking

Many graphs and pictures have been obtained from the new JET/EFDA databases (K. Musgrave) containing graphs and images ©Copyright protected by UKAEA/EFDA

The JET/EFDA intranet

Old colleagues still at JET, P. D. Morgan, E. M. Jones P. J. Lomas have helped refresh my memory

Jes Christiansen Culham Nov. 2005

CONTENT OF TALKCONTENT OF TALK Summary of the JET project’s history 1971-1999Summary of the JET project’s history 1971-1999 Building the JET tokamakBuilding the JET tokamak Scientific milestones in the JET projestScientific milestones in the JET projest Diagnostics & data Diagnostics & data Scientific records – results obtained in JET pulsesScientific records – results obtained in JET pulses D-TD-T campaign autumn 1997campaign autumn 1997 The futureThe futureLiterature:Literature:[1] [1] A European experiment, D. Willson, Adam Hilger Ltd. (1981)A European experiment, D. Willson, Adam Hilger Ltd. (1981)[2][2] Journal of Fusion Technology, Volume 11 (1987) dedicated to H. O. W Journal of Fusion Technology, Volume 11 (1987) dedicated to H. O. Wüüsterster[3][3] European experiment in Fusion, E. N. Shaw, North Holland (1990) European experiment in Fusion, E. N. Shaw, North Holland (1990)[4][4] The Science of JET, J. Wesson JET-R(99)13. The Science of JET, J. Wesson JET-R(99)13.

A brief historyof JET: the beginning

1971: The Euratom “Groupe de Liason” proposes that a very large tokamak should be built. Calculations suggest that a mega-ampere multi square metre cross section tokamak should reach ignition

1973: A team of 56 engineers and physicists☻ is established at Culham with the task of designing the “Joint European Torus”. Design is completed in autumn 1975 and described in EUR-JET-R5 report

1976-1978: Political disagreement over the siting of JET. A SAS mission to a hijacked German plane seals an agreement. Autumn 1978 “The JET Joint Undertaking” is created at Culham

The JET Joint Undertaking between EURATOM and UKAEA becomes the largest scientific project in Europe apart from CERN and ESA. Expected project period 1978-1990!☻M. L . Watkins is the only design team member left at JET

What is a joint undertaking?

In 1978 no one at Culham really knew or understood what a joint undertaking was. JET has been called a lot of names since then

“The Joint European Tours”

“ The joint undertakers”

etc.

We learned later that a Joint Undertaking by the Commission implies an institution without autonomy, i.e. no mainframe computer, no restaurant, no library, no tearooms

Torus hall 1979-80: basement has 60 000 t concrete

Several thousand lorry loads of concrete in autum 79

A brief historyof JET: the building and extensions

1979: Bulldozers and concrete mixers arrive. The JET team grows to some 650 members (260 UKAEA + 200 EURATOM + contractors).

1983: JET completed on time and to budget ( £120M basic form)

1983-92: Experimental campaigns. Results presented to three governing JET councils

1989: JET extended until 1992. A second extension until 1994 is itself extended to 1996

1995: The “final” extension until 2000 marks the end of a “sustained prolongation”

1998: The British staff case: Commission loses Court case The first 100 Euratom employees leave JET. In 1999: The last 100 Euratom employees leave. End of The Joint Undertaking EFDA

CONTENT OF TALKCONTENT OF TALK Summary of the JET project’s history 1971-1999Summary of the JET project’s history 1971-1999 Building the JET tokamakBuilding the JET tokamak Scientific milestones in the JET projestScientific milestones in the JET projest Diagnostics & data Diagnostics & data Scientific records – results obtained in JET pulsesScientific records – results obtained in JET pulses D-TD-T campaign autumn 1997campaign autumn 1997 The futureThe future

One of two flywheel generators 700MW to JETAt 300 rpm it would reach Newbury if let loose vertically!

One generator “got stuck” and put the project in danger. The Deputy Director P. H. Rebut fortunately found a way out.

Tokamak assembly starts 1982

One complete octant of vessel section, 4 TF coils and mechanical structure weighs just under 150 t such that the main crane can move it into the torus hall. First octant took 6 hours to move, last one ½ hour (steep learning curve)

The last octant slides into place between two limbs

A lot of expensive jigs and tools were used just once to assemble the tokamak

The inside of the JET vessel in 1983 contained only a limiter

Limiter

Porthole

In-vessel workers could enter vessel through portholes to carry out repairs, clean up surfaces, install new components. No special suits and breathing apparatus required

20 years later only the robot arm could enter for repairs

PINI’s removed from Neutral injection box

Plug In Neutral Injectors on JET were difficult to plug in. They have been operated with H, D, T, He3, He4 at energies from 80 to 160 keV. Maximum total power to plasma from two boxes each with 8 PINI’s: 23MW

Installation of first ICRH antenna 1985

The first limiter could be moved by manually cranking a handle outside the vessel

CONTENT OF TALKCONTENT OF TALK Summary of the JET project’s history 1971-1999Summary of the JET project’s history 1971-1999 Building the JET tokamakBuilding the JET tokamak Scientific milestones in the JET projestScientific milestones in the JET projest Diagnostics & dataDiagnostics & data Scientific records – results obtained in JET pulsesScientific records – results obtained in JET pulses D-TD-T campaign autumn 1997campaign autumn 1997 The futureThe future

Scientific milestones in the JET project (1)

1983: First plasma pulse with 15kA current in June 1984: ECE Te profiles. Scientists can now see what is going on

1985: ICRH antennae delivering up to 2MW

1986: First NBI beam box

1986: Separatrix plasma discovered during current decay H-mode

1987: The L-mode year, Belt limiter, no NBI

1988: 7MA pulse 17797, world record (P. J. Lomas). Beryllium

1989: The H-mode year, 2 NBI boxes, high speed pellet injector

1989: Full performance: pulse 20983, hot ion ELM free H-mode

Day 1: Directors waiting for first plasma

16 kA for 50msec

HO WüsterPH Rebut

A Saturday in June 1983

Scientific milestones in the JET project (2)

Oct. 1990: Lower hybrid heating installed

Oct. 1991: PTE, worlds first man made controlled releaseof fusion power: 1MW during 2s ELM free period in pulse 26148

1992-1994: Shutdown Feb. 92-Mar.94 for installation of Mk.I impurity divertor. Four internal divertor coils wound inside torus!

1995-1996: The divertor years. Edge, SOL, divertor physics boom

Oct. 1997: DTE, Full fusion power release of 16MW in pulse 42976

Mar. 1998: Mk II power divertor installed by JET’s in house state of the art robot arm

Apr. 1999: Last pulse 48382. Data from more than 20 0000 plasma pulses in the JET data storage system

20 years on: different vessel, different performance

Volume 120 m3, I 4 MA, B 4 T, P 20MW, tpulse 20sec

Hot plasma

The JET team

Almost half of the JET team came from Europe and were mostly Euratom employees

The UKAEA employees came from Culham (fusion), Harwell (diagnostics), Winfrith (shift technicians), CERN(computing)

During the construction phase the were many contractors

The project would provide for many facilities for team members both for work and socially , e.g. golf club

From 1983 a team spirit developed: many team members would work long hours and at weekends. Many repairs done during the night such that JET was ready next morning

The JET operations

Operations included: 1) planning session; 2) coordination meeting; 3) eight hour control room session

Control room sessions could be tense. Some dedicated team members became “control room junkies”

The average number of plasma pulses per day during 2 shifts is 20. The record is 48. The cost per pulse £20 000, so no goofs!

Control room observations control room speech JET jargon at the next JET Physics-Science Meeting.

The overhead projection of progress became the “hub” of the JET project. “Big events” e.g. 7MA or 20MW+, would generate a buzz in the control room which would soon fill up

CONTENT OF TALKCONTENT OF TALK Summary of the JET project’s history 1971-1999Summary of the JET project’s history 1971-1999 Building the JET tokamakBuilding the JET tokamak Scientific milestones in the JET projestScientific milestones in the JET projest Diagnostics & dataDiagnostics & data Scientific records – results obtained in JET pulsesScientific records – results obtained in JET pulses D-TD-T campaign autumn 1997campaign autumn 1997 The futureThe future

Big Science: the 14 MeV neutron spectrometer

This concrete shielding results in a massive weight and yields a collimated view of the plasma (M. Loughlin)

The 53 JET diagnostics produce: 0.2Mb (1983), 10Gb (2000) data. JET can not be operated without the magnetic diagnostic (control).

JET diagnostics: complexitiesIn the early 1980’es the starting cost of a diagnostic was in excess of £1M and would take one year + to complete because of complexities, space and routing of cables

A wooden scale model (1:20 3D) was used in addition to drawings to ensure there was access to diagnostic and no clashes with other parts of JET. ½ of wooden model now in Science Museum!

In the late 1980’es the IBM CAD system catia was used by the drawing office

Each diagnostic would normally be manned by a group of two to five scientists. An RO (Responsible Officer) would validate the data

Two examples of JET diagnostics

TTee by Thomson scattering (on by Thomson scattering (on JET) JET)

In the JET vessel a photon torpedo 10 cm (300picosec) long moves through the plasma and scattered photons are recorded as I(t) Te(R)

The optical length from plasma to roof top laboratory is 25m

TTii by charge exchange by charge exchange: : DD00++DD++DD++++DD00+h+h

JET

Emitted radiation h via optical fibres to CCD cameras Ti(R)

JET diagnostics: data recording

Each diagnostic transmitted analogue signals to CAMAC crates outside the torus hall.

Digitised signals were transmitted via optical fibres to computers: 1983 NORSK 100, 1992 SUN sparc workstations, i.e. no electrical connection to tokamak

All data was stored in the JPF (Jet Pulse File)

A suite of analysis programs read the JPF and produced PPF (Processed Pulse File). Results from inter-shot analysis shown on screens between pulses some 10 to 15 minutes after pulse.

In 1983 this was the worlds first fully integrated data analysis in fusion research and became the session guidance tool

The JET Intershot analysis and Storage system integrates the data from all diagnostics into one file

The role of JET data locally & internationally

Data in the CPF, Central Physics File, would show e.g.

Gradual degradation of window transmission of light

Co vs Counter NBI differences

Interferometer vs LIDAR differences

General trends in confinement physics

Data from the CPF would constitute a major part of the international Tokamak data bases established in 1990 and onwards

At the end of the JET project the data is still there for analysis

Examples of JET Data from PPF and CPF wil now illustrate the diversity of scientific experiments carried out

Distribution of JET data from > 20 000 pulses one data point x per pulse f(x)

Electron temperature RF power

Plasma energy Pulse rate

Lunch Dinner breaks

Plasma-performance parameters in JET have been stretched by an impressive factor of 10

The JET Monster sawtooth sawteeth stabilised

crash

Costley, Bartlett, Campbell of the ECE group supplied plenty of monsters

Edge physics of ELM types I & III. The LH & H L transitions and hysteresis

Edge ne [1019 m-3 ]

Pellet injection snake as m=1 density perturbation

The soft x-ray emission reveals (A.Weller 1988) the snake as a perturbation following a pellet making it to the q =1 surface

Many pellets many snakes PEP mode

With multiple pellets injected the density profile will peak. Additional heat (NBI & ICRH) yield an improved fusion performance because of the n2 T2 dependence of Pfusion

At t=5s the plasma current is still rising transient effect

Edge & SOL physics has been studied with probe array and IR imaging since the MK.I divertor was installed in 1992. Later new divertor geometries were tried with a divertor cryo-pump

Tomographic reconstruction (a) of soft x-ray emission shows precursor instability to a disruption; (b) shows the theoretically calculated form of the instability.

CONTENT OF TALKCONTENT OF TALK Summary of the JET project’s history 1971-1999Summary of the JET project’s history 1971-1999 Building the JET tokamakBuilding the JET tokamak Scientific milestones in the JET projestScientific milestones in the JET projest Diagnostics, data analysisDiagnostics, data analysis Scientific records – results obtained in JET pulsesScientific records – results obtained in JET pulses D-T campaign autumn 1997D-T campaign autumn 1997 The futureThe future

The D-T experiments October 1997

Careful planning began early 1997. Safety the major issue

The Tritium inventory arrived in a U238 bed from which it could be extracted by heating and to which it could be returned

A major feature of the DT campaign involved keeping track of the Tritium inventory. Models of T absorption in carbon tiles were developed

The campaign demonstrated that JET could be operated like a future fusion reactor

A measure of disappointment with the reaction of the world press

Dedicated issues of Nuclear Fusion (vol 39 no’s 2, 3, 8) include several JET articles describing features of these experiments

World record fusion power: JET pulse 42976 Oct. 1997

We had to wait fourteen years for these experiments!

Careful analysis with the TRANSP code by B. Balet & P. Stubberfield yield excellent agreement with measured data after 935 runs!

Pulse is anon steadystatehot-ion H-mode terminated by a giant ELM. Plasma energy is also a record.

16MW fusion power from 22MW input during 0.35sec

Thermonuclear fusion power calculations by TRANSP

Power densities in the (50%)D – (50%)T pulse 42976 show Pfusion Pinput

Electron power balance reveals first detectable P . The crowning achievement of the JET project!

The JET heating experiments

In a controlled series of experiments (P.E. Thomas) the Tritium concentration is varied from 0 to 80%. The heating of the electrons, i.e. Te , is the first demonstration of its kind. Great experimental care is required: constant power, start density etc.

Te

JET provides key data for the ITER design as regards size, plasma shape, confinement scaling, DT operation

Cross section of present EU D-shape tokamaks compared to the ITER project

JET

ITER

JET’s achievements

JET was built on time and to budget

JET is the largest tokamak in the world and since 1983 it has set most fusion records. The JET project has an excellent safety record

JET’s predicted performance parameters have all been exceeded except the most important one: Qfusion

It is the only existing device to use D, T, Be and observe fusion neutrons

Robot technology has proved that remote maintenance of a tokamak reactor is possible

1990: remove one octant to replace TF coil

When a TF coil failed several engineers and scientists predicted gloom and doom for the JET project. It was therefore a major achievement to saw up the vessel, remove an octant, disassemble it and change the faulty TF coil.

Has any other fusion device been subject to this treatment?

Lessons learnt

European collaboration at the £G level is of benefit to multi-disciplinary projects like JET: different problem solving approaches but all in English!

In-house products: state of the art (software, robotics, diagnostics)

The JET scientist-engineer collaboration with European industry was an outstanding success considering that almost all products were “one off” and certainly not off the shelf!

Lack of slow bureaucracy allowed for rapid changes to program

A £G project should be staffed by only project team members interacting with contractors

A successor to JET, proposed by Rebut and Bickerton 1989, should have started at the latest 1995. Ten years lost

When?Fusion Power

Typical Pulse duration

Q

1997 16MW 0.3 seconds 0.65 6MW 6 seconds 0.2

2015-2020 500-700MW 30 minutes 10

2030/40 1.5-2GW days/steady state 30

The future JET will one day become a green site[South Oxford District Council: planning permission 1979]

1985