Status of Material Load Experiments at MAMI inMainz

A. Ushakov1, S. Riemann2, G. Moortgat-Pick1, K. Alharbi 1,K. Aulenbacher3, S. Heidrich3, P. Heil3, Y. Tamashevich4

1University of Hamburg, 2DESY, 3University of Mainz, 4Helmholtz Zentrum Berlin

International Workshop on Future Linear Colliders (LCWS2018)

23 October 2018University of Texas at Arlington, USA

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 1 / 15

Outline

Motivation for material tests

Beam parameters of the Mainz Microtron and irradiated targets

Target temperatures (measured, maximal average, temperaturerise per pulse)

Estimations of thermal stress

Summary

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 2 / 15

Motivation

Motivation:

To check the target and exit window materials under expectedthermal load conditions at the ILC undulator-based positronsource.For instance, 7 mm thickness Ti6Al4V target cooled by radiation at 250 GeVcenter-of-mass energy has ≈470 ◦C average temperature and ≈510 ◦C peaktemperature (see S. Riemann talk).

Pulsed 14 MeV e− beam of the Mainz Microtron MAMI (50 µA, 2 ms pulses,100 Hz) was used to heat the 1 mm and 2 mm thick Ti6Al4V samples to〈T1mm〉 ∼ 600 ◦C and 〈T2mm〉 ∼ 700 ◦C with ∆T ∼ 70 ◦C that has resulted inswelling (see IPAC’17 proceedings TUPAB002).

Improved beam focusing system allows systematical studies of Ti-alloy(Grade 5) up to 450◦C average T and significantly higher temperature rise perpulse (up to 350◦C).

New wire scanner was used for the high accuracy beam size measurements.

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 3 / 15

Beam Focusing System and Target Holder

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 4 / 15

Beam Spot Size on Target

Beam size was measured at full (50 µA) current and very low repetition rate:σy = 42.8µm, σx = 66.3µm

0 50 100 150 200 250 300 350 400 450 500 550 600�10

0

10

20

30

40

50

Y [µm]

EventRate[kHz]

�y = (42,8±0,4)µm

0 50 100 150 200 250 300 350 400 450 500�20

0

20

40

60

80

100

X [µm]

EventRate[kHz]

�x = (66,3±0,5)µm

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 5 / 15

Energy Deposition Profiles on Beam Axis

0 100 200 300 400 5000

5

10

15

20

25

30

E [G

eV/(c

m3 e

- )]

z [µm]

Three target thicknesses were used: 200µm, 250µm, 500µm:thicker targets have higher average temperatures.

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 6 / 15

1-2 Oct. 2018: Logbook

50µA during pulse, 2.48 GHz (4.08 · 10−10 s bunch spacing)

200µm target thickness

1 1.5 ms, 10 Hz, 90 min., middle2 1.5 ms, 20 Hz, 40 min., top3 1.0 ms, 100 Hz, 40 min., bottom

250µm target thickness

5 1.0 ms, 120 Hz, 45 min., middle (radiation level is too high at f >120 Hz)6 0.5 ms, 140 Hz, 40 min., bottom

500µm target thickness

7 1.0 ms, 100 Hz, 40 min., middle (radiation level is too high at tpulse >1 ms)8 0.5 ms, 100 Hz, 40 min., top9 0.5 ms, 140 Hz, 40 min., bottom

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 7 / 15

Estimation of Emissivity

Calculated T vs Emissivity(200 µm, 1 ms, 100 Hz)

0.45 0.50 0.55 0.60 0.65 0.70

115

120

125

130

135

140

145

T [°

C]

Emissivity

Measured T

Measured and Calculated T vsDuty Factor (200 µm Target)

Calculated T

T tc [

°C]

Duty Factor

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 8 / 15

Average Temperature at Location of Thermocouplesand in the Middle of Beam

Temperature atLocation of Thermocouples

0.02 0.04 0.06 0.08 0.10 0.12

30

60

90

120

150

180

210

240

7.1 mm

7.1 mm

5 mm

7.1 mm

5 mm

7.1 mm

7.1 mm

Target thickness 200 µm 250 µm 500 µm

T tc [

°C]

Duty Factor

5 mm

Average Temperature inMiddle of Beam

0.02 0.04 0.06 0.08 0.10 0.12

100

150

200

250

300

350

400

450

Target thickness 200 µm 250 µm 500 µm

Max

Tav

e [°

C]

Duty Factor

5 mm and 7.1 mm indicate the distance from middle of beam to thermocouples

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 9 / 15

200 µm Target: Thermal Cycles

0.02 0.04 0.06 0.08 0.10

100

200

300

400

500

1 m

s; 1

00 H

z

1.5

ms;

20

Hz

200 µm thickness Tmax

Tave

Tmin

T [°

C]

Duty Factor

1.5

ms;

10

Hz

0.000 0.002 0.004 0.006 0.008 0.010 0.012

300

350

400

450

500

550

T [°

C]

t [s]

200 µm thickness1 ms, 100 Hz

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 10 / 15

Min, Ave and Max Temperature of 250 µm and 500 µmThick Targets

Temperatures of 250 µm Target

0.06 0.08 0.10 0.12

300

400

500

600

1 m

s; 1

20 H

z

0.5

ms;

140

Hz

250 µm thickness Tmax

Tave

Tmin

T [°

C]

Duty Factor

Temperatures of 500 µm Target

0.04 0.06 0.08 0.10

200

300

400

500

600

700

0.5

ms;

140

Hz

1 m

s; 1

00 H

z

0.5

ms;

100

Hz

500 µm thickness Tmax

Tave

Tmin

T [°

C]

Duty Factor

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 11 / 15

Temperature Rise per Pulse

0.02 0.04 0.06 0.08 0.10

100

200

300

400

1 m

s; 1

00 H

z1.5

ms;

20

Hz

200 µm thickness Tave

DTpulse

T [°

C]

Duty Factor

1.5

ms;

10

Hz

0.06 0.08 0.10 0.12

150

200

250

300

350

400

450

1 m

s; 1

20 H

z

0.5

ms;

140

Hz

250 µm thickness Tave

DTpulse

T [°

C]

Duty Factor

0.04 0.06 0.08 0.10100

200

300

400

0.5

ms;

140

Hz

1 m

s; 1

00 H

z

0.5

ms;

100

Hz

500 µm thickness Tave

DTpulse

T [°

C]

Duty FactorA. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 12 / 15

Equivalent von Mises Stress vs Peak Temperatureat the end of pulse

400 440 480 520 560 600 64080

100

120

140

160

1 ms, 100 HzDT = 230 °C

0.5 ms, 140 HzDT = 164 °C0.5 ms, 100 Hz

DT = 170 °C

1 ms, 120 HzDT = 231 °C

0.5 ms, 140 HzDT = 168 °C

1 ms, 100 HzDT = 242 °C

1.5 ms, 20 HzDT = 335 °C

Target thickness 200 µm 250 µm 500 µmEq

. von

Mis

es S

tress

[MPa

]

Tmax [°C]

1.5 ms, 10 HzDT = 347 °C

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 13 / 15

Distribution of Eq. Stress for 1 ms Pulses and 100 Hzat the end of pulse

200 µm Target∆T = 242 ◦C, Tmax = 554 ◦C

Max σvM = 157 MPa

500 µm Target∆T = 230 ◦C, Tmax = 618 ◦C

Max σvM = 125 MPaYield Strength σY [Ushakov et al. POSIPOL2018 talk]:

σY(T = 400◦C) ' 550 MPa,σY(T = 600◦C) ' 450 MPa

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 14 / 15

Summary

Ti-alloy (Grade 5) targets were irradiated by 3.5 MeV pulsedelectron beam at Mainz Microtron on 1-2 October 2018.

Estimated peak temperatures of irradiated samples were in therange between 400 ◦C and 600 ◦C as it is expected for the targetof ILC positron source.

Beam focusing system has allowed to obtain the relatively hightemperature rise per pulse (160◦C ÷ 350◦C).

Analysis of irradiated targets by laser scanning microscope will bedone during the next few days (after we will obtain them fromUniversity of Mainz).

"Material Tests" project supported by German Federal Ministry ofEducation and Research (BMBF) is close to the end (December2018).

A. Ushakov (University of Hamburg) Material Load Experiments at MAMI LCWS, 23.10.2018 15 / 15