NLC

Status and Milestones

D. L. Burke

ISG9KEK

December 10-13, 2002

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ISG9 OpeningD. L. Burke

Mission and Strategy

There is compelling reason to establish the X-Band technology soon.

– The international science community is taking on a 20-year mission to understand particle physics at the TeV energy scale.

– The LHC and a linear collider must have periods of concurrent operation to reinforce and guide each other, just as the case has been in the past.

– Construction and commissioning of a linear collider will take ~ 8 years.

Making a choice of linac technologies will enhance the probability that a linear collider is built and ready in time to meet this mission.

We must accelerate the demonstration of an X-Band rf system … and we must do it with no increase in level of funding.

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8-Pack Phase-I

klystrons

TE02

TE01

TE01

TE02

mode-preserving taper (TE02 cutoff at small end)

iris

Dual-Moded Pulse Compression System

mode mixer

cross potent

dual-mode directional coupler

load trees

reflective TE01 TE 02 mode converter / tuning plunger

jog-converter

dual-mode combiner

height taper

T/4

T/4

dual-mode-preserving taper

TE01

TE11or

TE01or

TE11(unSLEDed)

dual-mode splitter

bend -converter

circ-rect taper

E-plane bend

H-plane bend

TE11or

TE01(unSLEDed)

possible add-on

PPM Klystrons (75 MW 1.6 µsecs)

Dual-Mode SLED-II(4-fold compression in

time, factor 3.3 in power)

Power to loads in March 2003.

“Single Feed” RF Pulse(500 MW 400 nsec)

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NLC/JLC(X) SLED-II Baseline

• Phase-I of the 8-Pack will demonstrate the feasibility of a SLED-II rf system similar to that presently in use at the NLCTA.

• This demonstration will occur in 2003.

• JLC and NLC physicists presented to the world community (ILC-TRC) a SLED-II Baseline Design for an X-Band collider.

The “R1s”

» SLED-II Power Demonstration

» Structure Gradients

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The Test AcceleratorThe Test Accelerator

The NLCTA with 1.8 m accelerator structures (ca 1997).

Demonstrated ability to reach 500 GeV cms.

Accelerating gradient of 25 MV/m (loaded) with good wakefield control and energy spread.

Structures from KEK.

RF Power from SLAC

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X-Band RF Systems

NLCTASLED-II System

(1997)

– Conventional PFN modulator

– 50 MW/1.2s solenoid-focused klystrons

– SLED-II pulse compression

– 1.8m DDS structures at 40 MV/m

X-Band TeVSLED-II System(2002)

– Solid-state modulator

– 75 MW/1.6sPPM-focused klystrons

– Dual mode SLED-II pulse compression

– 0.9m DDS structures at 65 MV/m

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NLC/JLC SLED-II Baseline Test

NLCTA Housing

Solid-State Modulator

Solenoid-Focused Klystrons (to be replaced with PPM tubes).

Dual-Mode SLED-II

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SLED-II Demonstration Status

• Modulator is on-line and driving a pair of XL-4 klystrons.

• Third XL-4 klystron being installed, and fourth being conditioned in the Test Lab.

• All SLED-II designs passed microwave “cold tests” and components are in production.

On schedule for power tests to loads in March 2003.

Permanent magnet focused klystrons (one each from KEK and SLAC) scheduled for test in February.

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klystrons

TE02

TE01

TE01

TE02

mode-preserving taper (TE02 cutoff at small end)

iris

Dual-Moded Pulse Compression System

mode mixer

cross potent

dual-mode directional coupler

load trees

reflective TE01 TE 02 mode converter / tuning plunger

jog-converter

dual-mode combiner

height taper

T/4

T/4

dual-mode-preserving taper

TE01

TE11or

TE01or

TE11(unSLEDed)

dual-mode splitter

bend -converter

circ-rect taper

E-plane bend

H-plane bend

TE11or

TE01(unSLEDed)

possible add-on

Dual-Mode SLED IILow-Power (Cold) Tests

0

0.2

0.4

0.6

0.8

1

1.2

-200 -100 0 100 200 300 400 500

Reflected PulseInput Pulse

Ma

gn

itu

de

Time [ns]

320 ns

0

0.2

0.4

0.6

0.8

1

1.2

-200 -100 0 100 200 300 400 500

InputPulse Mag

Ma

gn

itu

de

Time [ns]

Input Pulse

(TE01)

First Reflection (TE02)

Second Reflection (TE01) 0

1

2

3

4

5

-2000 -1000 0 1000 2000

OutputInput

Po

we

rTime [ns]

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RF Pulse Heating

0

2

4

6

8

10 Distribution of Breakdowns(70 MV/m, 400 ns, 10 hr run)

T53VG3

RFRF

Beam’s eye view of input coupler.

SEM picture of input matching iris.Pulse heating in excess of 100° C.

Input coupler Output coupler58 Cells

Performance limited by pulse heating of coupler matching irises.

Rate in cells .1/hr

Autopsy performed after high-gradient testing.

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Mode Conversion (MC) Coupler

|Es|max= ~34 MV/m @ 48 MW

|Hs|max= ~98.4 kA/m @ 48 MW

Pulse Heating ~ 3° C

TM01 Mode Launcher

WC90

WR90

RF

Matching Cell

Mode Conversion Coupler

RF

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Unl

oade

d G

radi

ent (

MV

/m)

Time with RF On (hr)

Operations of T53VG3MC (Mode Conversion Couplers)

1Trip / 25 Hours

400 ns Pulse Width

1 Trip / 25 Hours

NLC/JLC Trip Requirement:< 1 per 10 Hours at 65 MV/m

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Test structures exceed the design goal of 65 MV/m for the JLC/NLC TeV collider.

Remains to complete fabrication and test of “NLC/JLC-Ready” structures with full detuning and damping.

• First tests of a/ = 0.18 structures (with bad couplers) look good, and testing of structures (with good couplers) is starting.

• Will start testing full-featured structures in May to satisfy TRC R1 items. There is a broadly-based line-up of structures in design and fabrication at SLAC, KEK, Fermilab, and CERN.

Schedule.

High-Gradient R&D Summary

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Bypass Linese.g. 50, 175, 250 GeV

X-Band Accelerator with Length for

500 GeV/Beam

32 k

m3.5 km

Injector Systems for 1.5 TeV

Why X-Band?

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NLC/JLC Energy Reach

The JLC/NLC Stage 2 design luminosity is

5 1033 cm-2 s-1 at 1.3 TeV cms.

CMS Energy (GeV)Site US Japan US Japan

Luminosity (1033) 20 25 30 25Repetition Rate (Hz) 120 150 120 100

Bunch Charge (1010)Bunches/RF PulseBunch Separation (ns)Loaded Gradient (MV/m)

Injected x / y (10-8)

x at IP (10-8 m-rad)

y at IP (10-8 m-rad)

x / y at IP (mm)

x / y at IP (nm)

x / y at IP (nm)

z at IP (um)

avePinch Enhancement

Beamstrahlung B (%)Photons per e+/e-Two Linac Length (km)

High Energy IP ParametersStage 1 Stage 2

500 1000

0.75

1.450

192

300 / 2

360

4

8 / 0.11

219 / 2.1

17 / 20

1.51

13.81.35.4

243 / 3.0

32 / 28

110

0.14

300 / 2

360

4

13 / 0.11

1.327.6

0.75

110

0.291.47

8.9

1921.450

Luminosity (1034

)

CM

S E

nerg

y (G

eV)

0 0.5 1 1.5 2 2.5 31000

1050

1100

1150

1200

1250

1300

1350

25 Bunches

192 Bunches

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Energy Goals

The energy reach of NLC/JLC is significantly greater than that of TESLA (for comparable cost).

This will be the central issue in the choice of technology.

– HEPAP 2001 “… 500 GeV … expandable to 800-1000 GeV …”

– ECFA 2001 “… 400 GeV …”

– ACFA 2001 “… initial 300-500 GeV … upgrade to greater than 1 TeV.”

The international community needs to reach a consensus on the importance of access to the highest energies.

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• “By the end of 2003, we hopefully should know if TESLA can reach 800 GeV at 35 MV/m.”

• “By the end of 2003, we hopefully should know if JLC/NLC can meet its main linac [TeV] RF system specifications.”

• “If yes, then the International Community could make a choice based on the other respective merits of these machines.”

ILC-TRC Interim ReportICFA

CERN, October 2002

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NLC-JLC Collaboration

Our job is to prepare for this technology choice.

• Complete the critical R&D (TRC R1 and R2)

• Update and document the X-Band Baseline design.

• Understand site requirements and cost estimates.

ISG9 will focus on this job.