2014/Nov./21
先端放射光源に関する研究会@分子科学研究所

極短周期アンジュレータ開発の現状
Present status of R&D forvery short period undulators

1. Target & Circumstances
2. Formation of a “very short period” undulator field
３. Field measurement & characterization
4. Recent achievements on magnet elongation
5. Summary
Photon Factory, KEK
Shigeru YAMAMOTO
山本 樹

1. Target & Circumstances
Hard x rays by shorter λu & lower (1st ) harmonics @ lower energy LS
In KEK we constructed the In-Vac Us to reduce the period length:

λu=12mm

In-vac Us (λu=4cm)@ 6.5GeV PF-AR (since 1989)
Gap=10mm

In-vac Short Gap Us (λu=1-2cm)@ 2.5GeV PF (2003-08)
Gap=4mmOther institutes: 3G LS (ESRF, APS, SPring-8):Compact 3G LS:

In-vac Us (λu~several cm)
In-vac Us (λu~2 cm)

1. Target & Circumstances

Short Gap Undulators @ PF
MakeiHc*λu

N12-keV photon

Kmax **

SGU#17 2003

25kOe

16mm

291.374

SGU#03 2005

30kOe

18mm

26

SGU#01 2008

28kOe

12mm

395th
5th
3rdName

1.684
0.781

* Magnet: NEOMAX TiN coated

What is the shortest λu?

** @ Gap

min=4.0mmTarget:
Very short λu = several cm (ordinary type) x 1/10= several mm (4mm)1. Target & Circumstances
Very short period Uundulators @ 2.5GeV LS

If these short gaps areallowed in the accelerator,
we have a new possibility.

2. Formation of a “very short period” undulator field:
perpendicular geometry
Direction of pulsed current

Electromagnet (2600V x 15kA)

Magnet plate
made of NdFeB(NEOMAX)

Perpendicular geometry:
Similar to a perpendicular magnetic
recording method in a recording mediaNSNλuS

2. Formation of a “very short period” undulator field:
perpendicular geometry
Magnetization #1
Magnetization #2
In a gap between
a pair of the magnets

NNS
λu

S2. Formation of a “very short period” undulator field:
A result of early stage attempts

Magnetizing head

Pole piece (expanded)
Magnetization test with
NEOMAX-48BH plate300

NO.1NO.2

Magnet size:

200

B (mT)

表100面
磁束0
密 -10
度-100(mT)

100mm x 20mm x 2mm
λu = 4mm
1030

50

70

90

Unsatisfactory !

-200

B ~ 150mT +/- 50mT-300
位置(mm)
Position(mm)λu/2 ~ 2mm +/- 0.6mm

2. Formation of a “very short period” undulator field:
fabrication of undulator magnets
Magnetizing a magnet plate driven stepwise
in the perpendicular geometry
λu/2Magnet (NMX-39EH)
SNSN

Back yoke (SS400)
Linear motor

Magnetizing head

Stepwise scan of λu/2

λu scan = 1st step of λu/2

SNSN

+ 2nd step of λu/2

NSNS

Accuracy in λu:

Wire spacing & step width

Accuracy in B-field:

λu & e- charge to the head

Linear motion is cntl’d by a closed loop scheme (+/- 3µm)

2. Formation of a “very short period” undulator field:
fabrication of undulator magnets
NMX-39EH
Br =12kG
iHc=25kOe

Field patternseen througha magnetic
fluid sheet

A pair of Nd-Fe-B magnets (TiN coated):
100mm long, 20mm wide, 2mm thick3. Field measurement & characterization

Measurement @ fixed gap=1.6mm

Hall probe ~1.3mm thick with 0.05 x 0.05 mm2 resolution
Gap > 1.6mm

３. Field measurement & characterization: continued
λu/2Magnet (NMX-39EH)

Magnetizing headSNSN

Back yoke (SS400)
Linear motor

Stepwise scan of λu/2

λu scan = 1st step of λu/2

SNSN

Measured undulator field (λu=4mm)@ gap =1.6mm+ 2nd step of λu/2

NSNSElectron orbit @ 2.5GeV:
end correction not made3. Field measurement & characterization: continued
Undulator field (λu = 4mm) of 4100G @ gap=1.6mm

Measured field is compared to ideal field with the same strength

4. Recent achievements
1. Magnet elongation by material improvement

100mm long= 25 periods

152mm long
= 38 periods

Field patternseen througha magnetic
fluid sheet

NMX-39EH TiN coated (Br =12kG, iHc=25kOe)
20mm wide, 2mm thick4. Recent achievements
2. Magnet elongation by connecting magnet plates.
Two plates are connected longitudinally.
Measurement is made at fixed gap of 1.6mm.

NMX-39EH TiN coated (Br =12kG, iHc=25kOe)
100 long, 20mm wide, 2mm thick5. Summary
We have been resolving major subjects and taking the right
direction to develop the very short period undulaotrs.
We can start preliminary tests to elongate magnet length.
Still we need further improvements in the magnetization especiallyfor both ends of the magnets, andprecise field measurement methods at a very short gap, etc.
However, we believe that evaluation experiments of the very shortperiod undulator based on the real electron beams will take placein the near future.
I am happy if this technology is useful to construct next generation
light sources.
JSPS Kakenhi
KEK-IMSS Intramural