PNCMI 2010, Delft, July 2010

Commissioning of the new Cryopad on POLI-HEIDI diffractometer in Garching (FRM II)

V. Hutanu, E. Lelievre-Berna, M. Meven, G. Roth, G.Heger

Institut für Kristallographie RWTH Aachen University, outstation at FRM II, TU Munich, Germany

PNCMI 2010, Delft, July 2010

• Introduction or a short history

• Motivation (SNP method)

• POLI-HEiDi Instrument

• Construction of the Cryopad

• Test and characterization

• Calibration on POLI-HEiDi

• First Experiment

• New Developments

Outline

PNCMI 2010, Delft, July 2010

Introduction (history of POLI-HEiDi)

2004: Start of the project to extend existing single crystal diffractometer HEiDi on the hot source at FRM II with polarized neutron option

2006: First SNP test experiment using MuPAD and 3He SFC in magic boxes on HEiDi

V. Hutanu et al., Neutron News 18(4), 14 (2007)

V. Hutanu et al. NIM A 612 (2009)V. Hutanu, et al, Physica B 397, 135-137 (2007)

PNCMI 2010, Delft, July 2010

Introduction (history of POLI-HEiDi)

2008: New nonmagnetic support goniometer; Decpol and nutators

V. Hutanu, et al, Physica B 404, 2633 (2009)

2010: POLI-HEiDi with installed Cryopad Decpol and Polariser

V. Hutanu, et al,……………. to be continued

PNCMI 2010, Delft, July 2010

Spherical Neutron Polarimetry (SNP)

• SNP uses vector characteristic of the neutron polarisation;

• SNP is performed in zero field so the polarisation does not precess, rotation as well as change of the polarisation due to interaction with the sample are analysed;

•SNP distinguishes polarisation rotation from depolarisation;

•Determination of the direction of the magnetic interaction vector;

• Examples:

- Unique solution of complex magnetic structures;

- Studies of magneto-electric domains;

-Determination of anti-ferromagnetic form factors;

It is based on the fundamental Blume-Maleev ecuations:

PNCMI 2010, Delft, July 2010

Spherical Neutron Polarimetry SNP

(P. J. Brown, Spherical Neutron Polarimetry, Ch. 5 “Neutron Scattering From Magnetic Materials, ed. T. Chatterji (2005))

PNCMI 2010, Delft, July 2010

POLI-HEiDi layout

POLI-HEiDi is using 3He spin filter both to create and to analyse neutron polarisation

Polariser

Monitors

Nutators

Slits

Decpol

3He spin filter cells

Detector

Sample CryopadCryostatBeamstop

λ/2 filters

Focusedmonochromatic beam

fromHEiDi monochromator

PNCMI 2010, Delft, July 2010

Cryopad construction

Original ILL design

Cooperation agreement and license contract:March 2007

Final delivery: June 2009

Cryostat: AS Scientif ic Ltd

Mu-metal screens: MS Ltd

Pecession coils: FZ Jülich, ILL

Nb Meißner screens:

HRS Titan; SDMS

PNCMI 2010, Delft, July 2010

Cryopad construction (precession coils)

First wiring: electric short Outgoing coil (second turn) Incoming coil

Destroying of the coil bodies by coating

Assembled precession coils,

(Happy end thanks to

E. Bourge-Lami ILL)

PNCMI 2010, Delft, July 2010

Cryopad tests and characterization

April 2009: Cryopad during the final vacuum tests at ILL

July 2009: Cryogenic test at FRM II after the reassembling

Results:

LHe consumption: cooling 70-80 l, operation: < 20 l/week, autonomy: 9 days (manual refilling)

LN2 consumption: cooling: 70-80 l, operation: < 1 l /h, autonomy: 20 h (automatic refilling)

Field captured inside the „zero-field“ chamber by the cooling in the optimal position < 2 mG

PNCMI 2010, Delft, July 2010

Cryopad calibration on POLI-HEiDi

Nov.-Dec. 2009 Cryopad on POLI-HEiDi at beam port 9b FRM II (λ = 0.87 Å)

SampleSampleSampleSample

RbMnF3 (P. Böni) at room temperature

(nuclear Brag reflections)

Measuring conditionsMeasuring conditionsMeasuring conditionsMeasuring conditions::::

2 x SFC pressure: 2.55 bar

Flipping ratio: 10

Cell replacement time: 5 min.

Polarisation time for 2 cells at Helios: about 3 h,Transmission of Cryopad:

> 90%

PNCMI 2010, Delft, July 2010

Cryopad calibration on POLI-HEiDi

Nutators

Incoming coil Outgoing coil

0.651(0.012)

0.025

(0.016)

0.009(0.016)

z

-0.021(0.016)

0.668

(0.012)

-0.033(0.016)

y

-0.014(0.016)

0.018

(0.016)

0.659(0.012)

x

RbMnF3 (711)

0.737(0.008)

0.022

(0.012)

0.044(0.012)

z

-0.012(0.012)

0.726

(0.008)

-0.005(0.012)

y

-0.028(0.012)

0.079

(0.012)

0.742(0.008)

x

RbMnF3 (-711)

z

y

x

Pout/Pin

First measured matrix

PNCMI 2010, Delft, July 2010

Cryopad on POLI-HEiDi control software

Mac based Igor Pro Cryopad control software used also at ILL, JAEA, HZB adapted for the TACO device control server used at FRM II.

- high stability and total flexibility

- remote controll of the all parameters

- the same commands as on D3, TAS 1, PF1- easy graphical data representation and handling

PNCMI 2010, Delft, July 2010

First experiment (HoNi2B2C)

Goals:

-To check all the commands and stability of the control software

-To test the Cryopad with a cryostat and to measure magnetic peaks

-To use FRM II magnet to control the domain distribution in the sample

-To perform SNP measurements using 2 SFC and to apply correction procedure

-To compare the performance of the POLI-HeiDi with new Cryopadwith D3 at ILL.

7.5 T Magnet at FRM II

100 mm Diam. room temperature bohr, fit with

the small close- cycle cryostat (4K <T<300K).

PNCMI 2010, Delft, July 2010

First experiment (HoNi2B2C)

Sample properties:

Crystal structure: body-centered tetragonal with I4/mmm space-group and the lattice a=b=3.51 Å and c=10.53 Å.

Superconducting transition temperature TC≈ 8.5 K

HoNi2B2C shows three types of antiferromagnetic structures in zero magnetic field in the narrow temperature range of 4.5 to 5.5 K:

a commensurate CM k1=0 0 1,

and two incommensurate ICM: ones k2=0 0 0.915 c*- structure k3=0.585 0 0 a*-structure.

PNCMI 2010, Delft, July 2010

First experiment (HoNi2B2C)

0.651(1)

0

0

Piz

0

0.658(1)

0

Piy

0

0

0.667(1)

Pix

-2.915

-2.915

-2.915

l

0

0

0

k

0

0

0

h

-0.006(11)0.060(11)0.018(9)

0.060(9)0.011(9)-0.011(9)

0.036(9)0.021(9)-0.660(9)

PfzPfx Pfy

0.615

0

0

Piz

0

0.622

0

Piy

0

0

0.64

Pix

-3.085

-3.085

-3.085

l

0

0

0

k

0

0

0

h

0.003(9)0.080(9)0.023(9)

0.065(9)0.015(9)-0.021(9)

0.026(11)-0.002(11)-0.636(9)

PfzPfx Pfy

0.592

0

0

Piz

0

0.601

0

Piy

0

0

0.604

Pix

-3

-3

-3

l

0

0

0

k

0

0

0

h

0.003(9)0.053(9)0.09(8)

0.065(8)0.011(8)0(8)

0.021(8)-0.002(9)-0.606(8)

PfzPfx Pfy

Polarimetry results on ICM c* reflections at 5.2 K

PNCMI 2010, Delft, July 2010

0 6 12 18 24 30 36 42 48

0,16

0,18

0,20

0,22

0,24

0,26

0,28

0,30

Data: A8Filling_ TrP8Model: TransmissionWeighting: y No weightin g Chi 2̂/DoF = 3.35 45E-6R^2 = 0.99425 P0 0.73628 ±0.00031T1 93.77402 ±0.22301

Tra

nsm

issi

on P

Time, h

HoNi2B

2C

Filling nr. 8; p= 2.37(1) barCell H4, T0 = 0.870(2)

Start: 18:23 (10.04.2010)End: 15:01 (12.04.2010)

First experiment (HoNi2B2C)

0.59

0

0

Piz

0

0.60

0

Piy

0

0

0.61

Pix

0

0

0

l

0

0

0

k

1

1

1

h

0.613(36)0.046(34)0.003(34)

0.056(32)-0.535(35)0.007(37)

0.014(32)0.055(46)-0.464(28)

PfzPfx Pfy

0.75

0

0

Piz

0

0.78

0

Piy

0

0

0.704

Pix

0.085

0.085

0.085

l

0

0

0

k

1

1

1

h

0.747(20)0.077(23)-0.012(23)

0.064(24)-0.773(24)-0.008(21)

-0.009(21)0.012(22)-0.711(19)

PfzPfx Pfy

6,7 6,8 6,9 7,0 7,1 7,2 7,3

0

2

4

6

8

10

12

14

Cou

ntin

g ra

te A

.U

l

5.2 K ( 007)

PNCMI 2010, Delft, July 2010

You are welcome to use it

2010: POLI-HEiDi with Cryopad (SNP) are available for users

PNCMI 2010, Delft, July 2010

Thanks

RWTH Aachen:G. Heger, G. Roth, A. Sazonov (LLB)

FRM II:M. Meven, S. Masalovich, J. Krüger, F. Gärtner

ILL:

E. Lelievre-Berna, E. Bourge-Lami, J. Brown

TUM:P. Böni, M. Janoschek (Univ. of California)

FZ Jülich:

R. Mueller, H. Schneider, T. Brückel

PSI:O. Zaharko