Emittance Measurements in MEBT-13 - Fermilab...1/11/2017 Q4-Scraper#02 Top / Buncher Off Ey=0.16...

Emittance Measurements in MEBT-13

J.-P. Carneiro et al.

PIP-II Technical Meeting

28 February 2017

Outline

• Introduction

– Beamline description, emittance measurement and simulation

details

• Emittance measurement at 5 mA

– Allison Scanner Vs Quad Scan

– Reconstruction of the Twiss parameters at the RFQ entrance

– Optics in MEBT

• Beam size at the Allison Scanner Vs TRACEWIN

• Beam size measurement along the MEBT Vs TRACEWIN

• Beam size measurement at Scrapers#02 Vs Buncher voltage

– Emittance Vs RFQ Field (57 kV, 60 kV and 65 kV)

– Emittance Vs Current (1 mA to 5 mA)

• Emittance measurement at 10 mA

02/28/2017J.-P. Carneiro, et al.| Emittance measurements in MEBT-1.32

PIP-II Injector Test Beamline


• Scrapers#01 and #02 are a set of 4 Scrapers Top, Bottom, Right, Left – Top (-10.2 mm), Bottom (-4.6 mm), Right (+1 mm), Left (+6.6 mm)

– Top (-10.2 m

(Top -10.2 mm, Bottom -4.6 mm, Right + 1 mm, Left +6.6 mm)

Introduction: Quad Scan Emittance Measurement Details


• Quad Scans are performed by measuring the RMS beam sizes at Scrapers#02

for different Q4 strengths. The beam current is monitored at the dump. Tests of

the MEBT Scrapers in the LEBT in 2015 showed that we could be confident in

the beam sizes measured by the Scrapers. The distance between Q4 and

Scrapers#02 allows emittance measurements in both planes (Hor. / Ver.)

• Beam Twiss parameters are reconstructed at the entrance of Q4 from the Quad

Scan analysis with no space charge. Quad calibration is 1.44 T/m at 1A.

• Automatic quad scan procedure developed by Bill Marsh in Sept. 2016.

: Transfer-matrix elements

Un-normalized emittance:

Twiss:

Introduction: Simulation Details


• In the present configuration of the beamline we do not have a reliable diagnostic to

measure the longitudinal beam parameters (bunch length and emittance).

• When reconstructing beam envelopes along the MEBT with simulations codes

(Tracewin/Track/Optim/Trace3D) the design longitudinal beam parameters are taken

into account.

Emittance measurement at 5 mA

Allison Scanner Vs Quad Scan


Maximum Allowed Emittance at the RFQ Exit at 5mA


From the PIP-II Conceptual Design Report, V1.00, Feb 28, 2017(Table 2.2, Page 9)

Note: The transverse emittance at 5 mA should stay below 0.2 mm-mrad.

Quad Scan Emittance Measurement at 5 mA


Measurement

Date

Measurement Techniques Reported beam parameters at the Q4 entrance

Emittance Beta Alpha

8/19/2016 Q4-Scraper#02 Left / Buncher On Ex=0.16 mm-mrad 6.9 mm/mrad -21.5

8/19/2016 Q4-Scraper#02 Top / Buncher On Ex=0.19 mm-mrad 3.1 mm/mrad 9.5

1/11/2017 Q4-Scraper#02 Right / Buncher Off Ex=0.17 mm-mrad 4.3 mm/mrad -12.3

1/11/2017 Q4-Scraper#02 Top / Buncher Off Ey=0.16 mm-mrad 2.5 mm/mrad +8.9

• Quad Scans performed on 8/19/2016 and 1/11/2017 for the same tuning of the

ion source and same beamline configuration

– Ion Source Extraction Voltage of 3.3 kV

– S1=138.2 A, S2=158 A, S3=238.3 A

– Q1=7.792A, Q2=6.428A, Q3=5.58A and Q4=4.96A

• LEBT neutralized up to the middle of Solenoid 2, then full space charge

• Buncher operating at 95 kV and -90 deg (8/19/16) and Buncher Off (1/11/17)

• RFQ operating at 65 kV

• 10 μs chopped pulse

“Lionel 5mA Settings”

Allison Scanner Phase Space Measurement as a Function

of Q4 at 5 mA (data of 01/11/2017)


Q4=3.06A Q4=3.26A Q4=3.46A Q4=3.66A

Q4=3.86A Q4=4.06A Q4=4.26A Q4=4.46A

Q4=4.66A Q4=4.86A Q4=5.06A Q4=5.46A

Allison Scanner Vs Quad Scan Emittance Measurement at

5mA (data of 01/11/2017)


• The negative error bars on the measured Allison Scanner emittances account for

a 5% slit width correction (Lionel’s 02/28/17 talk, Slide 15)

• Allison Scanner emittance vary by ~10% as a function of Q4

• Allison Scanner and Quad Scans agree within 10% at 5 mA.

Reconstruction of the Twiss parameters at the RFQ entrance



Reconstruction of the Twiss at the RFQ exit / MEBT entrance

(Sunny’s suggestion)

Step1: Find Twiss at Q4 entrancefrom Quad Scan (no space charge)

Alpha X/Y = -12.3/8.94Beta X/Y = 4.26/2.47 mm/mradEmit X/Y = 0.17 /0.16 mm-mrad

Step2: Re-work the Twiss with TRACEWIN/TRACK(at 5mA) to mimic the beam sizes from Quad ScansAlpha X/Y = -12.3/8.94 Alpha Z= -3.11Beta X/Y = 4.36/2.43 mm/mrad Beta Z = ~6 m/radEmit X/Y = 0.17 /0.16 mm-mrad EmitZ = 0.22

Step 3: Matching with TRACEWINat 5mA from MEBT entrance to Q4

Alpha X/Y = 1.63/0.05Beta X/Y = 0.46/0.14 mm/mradEmit X/Y = 0.17 /0.16 mm-mrad

AlphaZ=-0.37BetaZ=1.12 mm/mradEmitZ=0.22 mm-mrad

Note: backpropagation with OPTIM/TRACK currently in progress.

Twiss at RFQ entrance: Expected Vs Reconstructed Twiss


Alpha X BetaX

mm/mrad

Emit X

mm-mrad

Alpha Y Beta Y

mm/mrad

Emit Y

mm-mrad

TRACK 3D with 5mA

WB and RFQ at 65 kV

-0.21 0.28 0.16 -0.05 0.12 0.16

Reconstructed Twiss 1.63 0.46 0.17 0.05 0.14 0.16

• The Table below shows the Twiss parameters at the RFQ exit as predicted by

TRACK with 65 kV of inter-vane voltage and the Twiss parameters as

reconstructed from the Quad Scan (01/11/2017, 5mA, buncher off) using the

technique described in the previous slide.

• In TRACK a 3D model of the RFQ built with MWS is used. The input distribution

is Waterbag at 5 mA with :

– Alpha X/Y = 1.6, Beta X/Y = 7 cm/rad, Emit X/Y = 0.135 mm-mrad

• Predicted longitudinal Twiss at the RFQ exit (at 65 kV, from TRACK) :

– Alpha Z = -0.37, Beta Z = 1.12 mm/mrad (774 deg/MeV), Emit Z =0.22 mm-mrad


RMS Beam Sizes Measured at Scrapers#02 Left and Top

Vs TRACEWIN at 5mA (data of 01/11/2017)

• TRACEWIN uses as input Twiss parameters the Reconstructed ones reported in

the previous table. The TRACEWIN input distribution is a 6D Gaussian cut at 3

Sigma. Simulations start 350 cm from the middle of Q1.

• The good agreement between the measurements and TRACEWIN shows that

our model is self-consistent.

Optics in MEBT

Beam size measurement at the Allison Scanner Vs TRACEWIN

Beam size measurement along the MEBT Vs TRACEWIN


Allison Scanner Hor. Beam Size Measurement Vs

TRACEWIN at 5 mA (data of 01/11/2017)


• The measured and simulated beam sizes agree within 6-7%.

• 5% error bars are implement in the Allison Scanner beam size measurements

• The Allison Scanner entrance slits are ~18 cm from the Q4 exit.

Measured beam sizes along the MEBT Vs TRACEWIN at

5mA (data of 01/10/2017, Sasha & Bruce)


• On 01/10/2017 the RMS beam sizes have been measured at the Scrapers#01 and

Scrapers#02 (Top, Bottom, Right, Left) and at the Allison Scanner. Standard optics.

• The measured beam sizes are consistent with TRACEWIN predictions (taking the

reconstructed Twiss parameters at the MEBT entrance) at the exception of the beam sizes

measured at Scrapers#01 Right/Left.

Beam size measurement at Scrapers#02 Vs Buncher voltage



Measured / TRACEWIN RMS Horizontal and Vertical Beam

Sizes at Scrapers#02 as a function of RF Buncher Voltage

• On 08/23/2016 we measured the RMS beam size at the Scrapers#02 Left and Top as a

function of the RF Buncher Voltage (0kV to 130 kV).

• For standard optics in the beamline at 5mA.

• Agreement between measured beam sizes and expected from TRACEWIN is reasonable

at the exception of the horizontal beam size at low buncher voltage.

• Previous energy measurements show a proper calibration of the buncher voltage.

HORIZONTAL (Scraper #02 Left)

VERTICAL (Scraper #02 Top)

Measured Emittance at Allison Scanner Vs RFQ Field

(57 kV, 60 kV and 65 kV)


Emittance at the Allison Scanner Vs RFQ Field at 4 mA

(data of 01/11/2017-PM, Bruce)


RFQ at 57 kV (~3.8 mA)Emittance ~0.32 mm-mrad



• TRACK RFQ simulations (right plot) with

Waterbag input distribution

• Transmission from TRACK is expected to start

dropping at ~55 kV

• TRACK predicts that the long. emittance at 65 kV

may be few percent lower (~5 %) than at 60 kV.

98%54%

5%

Transmission(from TRACK)


Measured Emittance at Allison Scanner Vs Beam Current

(1mA to 5mA)


Allison Scanner Emittance Measurement a the MEBT Vs

Beam Current (data of 01/20/2017).

• On 01/20/2017 we measured the emittance at the MEBT Allison Scanner for different

current (1 mA to 5 mA) by adjusting the extraction voltage at the Ion Source.

• No retuning of the MEBT was necessary. 100% transmission was measured at the dump

for all currents. The Twiss parameters at the RFQ exit are expected to not change much

as a function of the beam current.

• TRACEWIN simulations performed by Sunny taking the measured phase space at the ion

source exit as input distribution (built with PLOTWIN) with optimal neutralization in LEBT


Measured Emittance at 10 mA

Allison Scanner Vs Quad Scan

Calculated Transverse and Longitudinal Emittance Vs

Current at RFQ Exit (J. Staples PARMTEQM simulations)


From the PIP-II Conceptual Design Report, V1.00, Feb 28, 2017(Fig. 2.6 Page 14)

Note: The transverse emittance at 5 mA and 10 mA is expected to not change.The longitudinal emittance is expected to increase from 5mA to 10 mA.

~0.15 mm-mrad~0.15 mm-mrad

~0.22 mm-mrad

~0.26 mm-mrad

Quad Scan Emittance measurement at 10 mA


Measurement

Date

Measurement

Techniques

Reported beam parameters at the Q4 entrance

Emittance Beta Alpha

8/16/2016 Q4-Scraper#02 Left Ex=0.3 mm-mrad 3.6 mm/mrad -10.4

8/16/2016 Q4-Scraper#02 Right Ex=0.28 mm-mrad 3.9 mm/mrad -11.1

8/16/2016 Q4-Scraper#02 Top Ey=0.33 mm-mrad 2.1 mm/mrad +7.7

8/16/2016 Q4-Scraper#02 Bottom Ey=0.31 mm-mrad 2.1 mm/mrad +7.4

1/18/2017 Q4-Scraper#02 Right Ex=0.28 mm-mrad 4.6 mm/mrad -12.6

• Quad Scans performed on 8/16/2016 and 1/18/2017 for the same tuning of the

ion source and same beamline configuration

• S1=151.4A, S2=216.5 A, S3=230.9 A

• LEBT neutralized up to the middle of Solenoid 2, then full space charge

• Q1=7.792A, Q2=6.428A, Q3=5.58A and Q4=4.96A

• Buncher operating at 95 kV and -90 deg

• RFQ operating at 65 kV

• 10 μs chopped pulse

Allison Scanner Emittance measurement at 10 mA


Allison Scanner Phase Space ~ 10 mA, Q4=4.96 A

Emittance ~0.33 mm-mrad Q4 [A] Emittance at

Allison Scanner

4.96 A 0.33 mm-mrad

4.86 A 0.32 mm-mrad

4.66 A 0.31 mm-mrad

4.46 A 0.33 mm-mrad

4.26 A 0.33 mm-mrad

4.06 A 0.33 mm-mrad

3.86 A 0.33 mm-mrad

Summary


Transverse Emittance Measurements

• Emittance at 5 mA at optimum conditions has been measured between 0.17-

0.19 mm-mrad which fulfils the 0.2 mm-mrad requirement for PIP-II.

• First emittance at 10 mA has been measured at around 0.3 mm-mrad.

• Changing the extraction voltage of the Ion Source from 3 kV to 5 kV allows to

efficiently adjust the beam current (< 5mA) with full transmission and low

emittance measured in the MEBT. No retuning of the MEBT necessary.

• Emittance measurements performed with the Allison Scanner and Quad Scans

agree within 10% at 5 mA and 10-20% at 10 mA.

Optics Measurements

• An attempt to reconstruct the Twiss parameters at 5mA at the RFQ exit / MEBT

entrance shows a reasonable agreement with the expected Twiss. Reconstructed

Beta function in the horizontal plane still twice larger than expected.

• Measured beam sizes at 5 locations along the MEBT agree within 6-7% with

TRACEWIN at the exception of the beam sizes at Scrapers#01 (Right/Left).

• Transverse defocusing from Buncher cavity is properly modelled with TRACEWIN.

Emittance Measurements in MEBT-13 - Fermilab...1/11/2017 Q4-Scraper#02 Top / Buncher Off Ey=0.16...

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