report on the meeting of itpa tg steady-state operations and itpa tg transport proposal

F P Orsitto ENEA Frascati

12th ITPA Princeton march 07 1

Report on the meeting of ITPA TG Steady-State Operations

and ITPA TG Transport proposal

Francesco Paolo Orsitto

ENEA C R Frascati



contributions

• G Sips, T Luce

• N Hawkes, C Maggi

• E Doyle



Outline

• ITPA SSO :• i) Summary of arguments discussed • ii)Messages to TG Diagnostics

• ITPA TG Transport : proposal for detailed design of turbulence measurement set for ITER

( possibly to be discussed in detail in the session on measurement requirements,Thursday morning )



Summary of ITPA SSO Meeting



Arguments discussed

• ITER Design Review : Issue cards( including issue cards presented by A Costley and R Boivin)

• High Priority tasks

• Modelling:simulation of core-pedesal-divertor plasmas

• MHD in Hybrid scenarios (Joint Meeting w ITPA MHD)

• Pedestal physics (Joint Meeting with ITPA Pedestal)

• Actuators and modelling

• Real Time plasma control

• ITPA Joint experiments



SSO TG: High priority tasks for 2006/2007(Not in order of priority)

1. Continue the focussed modelling activity on ITER Hybrid and Steady state scenarios, using standard (and common) sets of input data.

2. Assess requirements for real-time control in ITER and increase collaboration in joint experiments on real time control.

3. Pedestal studies: Experiments to document pedestal in advanced scenarios, modelling of pedestal, pedestal conditions in ITER (maximum Tped).

4. Code benchmarking of LHCD and NBCD and implications for ITER.

5. The current rise of advanced scenarios, in particular requirements for the ITER start up phase. Questions to TG Diagnostics



edge studies

Steady State Scenario studies should have a stronger overlap with edge

studies, as the edge plays an important role in advanced scenariosPublication at the IAEA by C. Maggi (AUG):

“Characteristics of the H-mode Pedestal in Improved Confinement

Scenarios in AUG, DIII-D, JET and JT-60U”



Hybrid definition: Summary of SSO discussion

1. So far data has been provided to the confinement databases that are hand selected. Data from JET, DIII-D, AUG and JT-80U.

2. H98 should not be used to select the data.

3. With the ITER target for Hybrid operation or Q>10 a selection on beta can be made. Either a fixed value: N > 2.5. Or better: At q95 ~ 4.5, N > 2.7, At q95 ~ 3.2, N > 2.2.

4. Plasma inductance is strongly correlated with beta. Both beta and li can not be used. Use of beta is preferred.

5. The resistive diffusion time (R) should be a variable in the database. Allows selection of pulses that achieve high beta with relaxed q-profile. (Or an indication on the change of the current profile during the time window selected)



Observations of TG SSO for the attention

of TG Diagnostics



Measurement availability during current rise

• 1. The diagnostic availability during the current rise phase. Both diagnostic beam and heating beams may not be available.

• 2. The heating beams: The SSO group is concerned on the requirement to have both heating beams for complete diagnostic measurements.



2 Heating Beams + 1 optional: (HNB)

• (1 MeV D2 modulated)

• HNB are : voltage modulation

• 1 Diagnostic Neutral Beam (DNB)

• (100 kev H2 1-3 s every 10-20s)

• DNB is independent but not continuous

• Beam cross section 30X30 cm2.

ITER Neutral Beams



ITER requirement on MSE measurements



MSE diagnosticHNB4

HNB5

eqport3

eqport1

center is covered by NHB4 edge by HNB5So both beams must work toHave a complete coverage of plasma



DNB is used by CXRS systems



Spatial resolution of the diagnostic

Spatial resolution requirement (a/20 = 10 cm) is not satisfied everywhere

it remains under 15 cm everywhere, and better than a/40 around rho= 0.2 and 0.65



MSE diagnostic on DNB

A MSE diagnostic using ratiometry method is proposed as a complement to CXRS on DNB (M. von Hellermann).

•Two observation ports for central MSE and edge MSE

•Spatial resolution requirement satisfied.

Eport3LOW_DNB4

0

20

40

60

80

100

120

6200 6600 7000 7400 7800 8200

Radial position of observation point (mm)

Sp

atia

l res

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(mm

)

-40

-20

0

20

40

60

80

Do

pp

ler

shif

t (A

)

Uport3_DNB4

0

50

100

150

200

6200 6600 7000 7400 7800 8200

Radial position of observation point (mm)

Sp

atia

l res

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(mm

)

-120

-100

-80

-60

-40

Do

pp

ler

shif

t (A

)



MSE availability

• No heating beam will be available for early part of current rise (ne < 4x1019m-3).

• Scenario development and control require routine MSE measurements.

• Hence there is a concern on q(r) availability during current rise.



MSE measurements in AT scenario

• AT scenario would require off-axis shift NNBI

• How about MSE measurements and central q determination in this condition?

• Would the polarimetry do the job?



MSE meas vs NNBI power modulation

• It has been decided to carry out the power modulation of NNBI by accelerating voltage change, (modulation of 800kV-1MV, in 100ms).

• How about impact on MSE measurements?



TG DIA to answer about Availability of measurements during current ramp up

TG OSS to assist in plasma scenario evaluation

• 1.What about the diagnostics beam availability during the current rise?

• 2.Which measurements will not availed without any beam heating or with just 1 heating beam.

• 3.Accuracy of the q-profile determination during the current rise



Measurements in new scenarios

• Physics requirements:• qmin = 2 at 9MA : To give access to AT scenarios

with Q~5• qmin = 1.5 at 12MA: To allow Hybrid scenarios

with 1 < qmin< 1.5 for long pulse component testing in ITER.

• qmin > 1 at 15MA: To establish discharges with Q > 10 potential, or give more margin for primary design goal.



Measurements

• These scenarios are different from what is current proposed and have different (more strict?) requirements on availability of plasma equilibrium and q(r) profile information.



ITPA TG Transport Proposal



Physics justification for detailed design of turbulence measurement set

for ITER

Goal: Raise priority of turbulence measurements on ITER, such that possible measurement approaches are defined and detailed machine interface design performed.



Desired measurement set

• (1) Survey capability: Ability to continuously monitor turbulence in 0<ks<1 wavelength range across plasma diameter. Need not have significant radial localization.

• (2) Detailed local measurements: Local measurements of fluctuation amplitudes, correlation lengths, S(k), and poloidal turbulence flow velocities at multiple and/or variable locations across plasma radius, from core to edge. A broader wavelength coverage, such as 0<ks<6 is also desirable, so as to measure wavelengths relevant for electron transport. Measurement of several fluctuation fields is also desirable.



Physics justification

• Establishing a full theory-based understanding and predictive capability for transport in burning plasmas. Only turbulence measurements can provide fundamental verification and validation of theory/modeling.

• New turbulence/transport interactions are possible in a burning plasma with dominant alpha heating. For example, any prompt core alpha loss will generate a radial electric field and hence generate ExB field shear, leading to turbulence suppression, and enhanced alpha production.

• Localized fluctuation diagnostics are essential for studies of energetic particle and Alfven mode physics in ITER. The study of such modes and their potentially critical effect on alpha confinement is an essential component of the ITER physics program.



conclusions

• Interesting contacts with ITPA TGs at Meetings after IAEA Chengdu.

• Two messages :

• TG SSO concerned about the measurements of MSE during current rise

• TG Transport : priority to be increased on fluctuation diagnostics



Slides for discussion



Issue card1: Decision on Additional Heating

Upgrade( A Costley) • Action Implied for the Design Activity: Decide now on the option

for the additional heating upgrade (73 MW -> 110 MW), that is third NB or additional RF.

• Re the HB issue (diag issue #1).

• The point is that if we carry the option of beams or RF for the planned auxillary heating upgrade into the operation, and then subsequently chose the RF, we will have a far from optimum use of the ports. We could effecetively lose two ports (one at the mid-plane and one at the upper level). If, on the other hand, we choose to upgrade the beams, we will lose a lot of operation (maybe one year).

• Making the decision now, enables us to optimise the use of the ports and the operation. The decision has to be made at some stage and so why not now.



Issue #1

• Currently mid-plane ports 4, 5 and 6 are set tangential to take NBs. • Port 7 is occluded by the tangential port 6 and has very limited use. • Upper ports, 4, 5, 6 and 7 are also topologically in the NB Cell and so

will have restricted use, possibly severely restricted. • The option of using port 6 for a neutral beam severely disables

equatorial port 7 and upper port 7, whether a neutral beam is ever installed there or not.

• If it is decided during the operation programme to add the third NB there will be minimal impact on other systems, although probably a significant down time to install it (one year?). Because of this delay, it is not clear if such a retrofit is feasible.



Issue #1

• On the other hand, if it is decided to upgrade the RF systems during the operation, then the plan is that the diagnostics currently in port 11 will be relocated into the tangential port 6.

• This has several disadvantages:• (i) the diagnostics will probably have a reduced capability in this port,• (ii) they will be located in the NB cell with the potential attendant

problems of contamination and activation, and • (iii) they will require special provisions (extra cost) for handling and

maintenance. • This will be a far from optimum use of the ports. The machine and the

programme will suffer the disadvantages and the cost of three tangential ports but only get the benefit of two.



Issue card 4:Specifications of the diagnostic neutral beam( R Boivin)

• The primary motivation for the DNB is• the light ion and He ash measurement via CXRS. • the beam will also be used for ion temperature and rotation

measurements.

• Presently the requirements on the DNB have not been optimized:• Of particular concern is the proposed duty cycle and pulse length which

do not allow continuous measurements during the ITER pulse.

• This would also prevent scenarios where rotation control using the CXRS/DNB measurements is needed for long periods and/or with sufficient time response.

• the parameters of the DNB (specifically non continuous operation) may not allow the use of CXRS as a control measurement.

• Question:could the DNB spec be changed to make it possible?



Issue card 5:Specifications of the (heating) beams( R Boivin)

• Action Implied for the Design Activity: • Is there a limitation on current drive control due to the current

configuration of the MSE diagnostic that uses both heating beams?

• The heating beams serve for heating, current drive and rotation control. • the 2 beams will be used for the MSE diagnostic . • Since only 2 beams are presently envisioned :• the actuators and sensors are based on the same element, namely the

heating beams, if the MSE measurement is used in feedback control. the lack of a beam for physics and/or control reason would represent the lack of a measurement and create potentially difficult situations.

report on the meeting of itpa tg steady-state operations and itpa tg transport proposal

Documents

itpa pedestalactuators

outline itpa sso

jt60u12th itpa princeton

summary of itpa sso

sso tg

iter hybrid

observations of tg sso

iter target