Proceedings of IBIC2012, Tsukuba, Japan

THCB02TWISTING WIRE SCANNER
V. Gharibyan∗ , A. Delfs, I. Krouptchenkov, D. Noelle, H. Tiessen, M. Werner, K. Wittenburg
Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
A new type of ’two-in-one’ wire scanner is proposed.
Recent advances in linear motors’ technology make it possible to combine translational and rotational movements.
This will allow to scan the beam in two perpendicular directions using a single driving motor and a special fork attached to it. Vertical or horizontal mounting will help toescape problems associated with the 45 deg scanners. Test
results of the translational part with linear motors will bepresented.

INTRODUCTION
Wire scanners serve as an essential part of accelerator diagnostic systems and are used mostly for beam transverse
profile measurements (for a review see [1]). Dependingon scanning wire trajectory the profilers could be classified as rotational [2] or linear [3]. When its necessary tomeasure vertical and horizontal beam profiles at the samelongitudinal position one has to use two independent scanners. Alternatively two profiles could be sampled by using
a single driver mounted at 45deg with two wires stretchedhorizontally and vertically over a fork attached to this linear driver. However, wire vibration in the scanning direction is a known problem for the 45deg scanners [4, 5].
Different types of driver motors have been employed inusing a single linear-rotary motor and a simple wire hosting
construction attached to it. The construction is a key-likewire holder which makes twisting (helical) motion during
a 2-D scan. Next will follow a more detailed description ofthe translational part with linear motors. In conclusion wewill estimate technical feasibility of the proposed twisting
scanner.

LINEAR-ROTARY MOTORS
A linear-rotary motor produced by company LinMot [6]is shown in Fig. 1. The motor consists of a linear and arotary part merged together. Translational and rotationalmotions are decoupled and organized independently. However, linear and rotary motion synchronization is foreseen
by motor controller logic. The motors are provided indifferent configurations with variable sizes and strengths
reaching up to 1 kN linear force and 7.5 N m rotating torque. Motor controllers use advanced and flexible
Table 1: LinMot PR01-52x60-R/37x120F-HP-100 Linearrotary Motor Parameters
Parameter

Value
Linear Motion

Extended Stroke ES mm (in)Standard Stroke SS mm (in)Peak Force E12x0 - UC N (lbf)
Cont. Force N (lbf)
Cont. Force Fan cooling N (lbf)
Force Constant N/A (lbf/A)
Max. Current @ 72VDC A
Max. Velocity m/s (in/s)
Position Repeatability mm (in)Linearity %100 (3.94)
100 (3.94)
255 (57.3)
51 (11.5)
92 (20.7)
17 (3.8)15
3.9 (154)±0.05 (±0.0020)±0.10

Rotary Motion

Figure 1: Linear-rotary motor from LinMot company.
order to move and control scanning wires which are normally mounted on cards or forks connected to the motors.
Stepper or servo rotating motors are among the most popular drivers and linear motors are at developing stage. Here
we explore commercially available translational-rotational
motor units to propose a wire scanner solution which will
perform beam scans in mutually perpendicular directions∗ vahagn.gharibyan@desy.dePeak Torque Nm (lbfin)
2 (17.7)
Constant Torque (Halt) Nm (lbfin)
0.5 (4.4)
Max. Number of revolutions Rpm
1500
Torque Constant Nm/Arms (lbfin/Arms) 0.46 (4.07)
Max. Current @ 72VDC Arms
6.2
Repeatability deg±0.05
software/firmware which should help to perform slow or
fast scans with minimal programming efforts. An operational voltage of 72VDC and maximal current of 15A
complies to general Electro-Magnetic Interference (EMI)requirements in accelerator environments. Described features make the linear-rotary motor as an attractive toolfor driving the proposed twisting wire scanner. A closer

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1c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Abstract

THCB02

Proceedings of IBIC2012, Tsukuba, Japan

look to specifications of a linear-rotary motor LinMot
PR01-52x60-R/37x120F-HP-100 is presented in Table 1 as
an example. Listed values for the Repeatability are quotedfor built-in, internal position and angle sensors. One canimprove these parameters considerably by using external,
finer sensors which is foreseen by controller software. In
following we demonstrate that for linear motors.

3-D KEY-BIT HOLDER FOR 2-D FASTSCANS
An improved, slightly more complicated design, for thefast scans could be achieved by tilting the second quadrant

KEY-BIT SCANNER

c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○In order to apply 2-D helical motion of a linear-rotary
motor for scanning a beam, one needs to invent a suitable construction with stretched wires and a holding frame
which stays out of (does not cross the) beam during thescan. For that we propose a key-bit like assembly which
fulfills above requirements. The construction is schematically presented in Fig. 2. As it’s indicated by arrows,

Figure 3: Scanning scheme of a three dimensional keybit wire holder. Vertical green line depicts the beam to bescanned.

Figure 2: A key-bit holder scheme with horizontal and vertical scanning wires. A small ellipse on the right depicts abeam running normal to the page.
for this arrangement translational motion will first scan thebeam in horizontal direction and next, when the beam will
be inside the key-bit, a proper rotation will perform verticalscan. It is necessary to limit the rotation angle in order toescape crossing of the wire holder with the beam. For that
there is sufficient space between the holder frame and thebeam, remaining after the rotational scan is over. Denoting
vertical key-bit and wire size by L and lw respectively, thebeam to holder distance could be expressed asxx
L arccos − arccos
Llw
where x is distance between the beam and rotational axis.
Applying this formula for fast (> 1 m/sec) rotationalscans with some realistic accelerator parameters we obtainsufficient space to accelerate the wire while for deceleration the space is limited and one needs to use mechanicaldumps to stop the scanner.

of the key-bit wire holder out of the construction’s planeby some angle. A 90 deg tilted key-bit holder is sketchedin Fig. 3. Scanning sequence is exactly the same as for theflat key-bit scanner with an advantage of more room after
the second scan is over. This should give sufficient time
to decelerate and stop the frame by the motor alone, without mechanical dumpers. In addition the tilted key-bit’s
moment of inertia is considerably smaller than in flat case.
This will allow easier and improved handling of rotations
with more ergonomic acceleration and deceleration of thekey-bit structure.

LINEAR MOTOR PERFORMANCE AS A
SCANNER DRIVER
We are developing wire scanners with linear motor
drivers for European XFEL accelerator. Here we present
some of the results obtained during recent laboratory experiment with test scanners. Planned test setup is displayed inFig. 4 while experimental realization is presented by Fig. 5.
For horizontal and vertical scans two identical and independent profilers are mounted to a special vacuum chamber
dedicated to beam transverse diagnostics.
Position feedback for the linear servo-motor is provided
by an external Heidenhain optical system which is accurate to 1µm. With the setup we have tested triggered fastscans and mechanical as well linear motors performance
during/after tens of thousand scanning strokes. Important
specifications of the XFEL wire scanners are shown in Table 2. Tests have marked most of the listed specifications asISBN 978-3-95450-119-9
2Transverse Profiles, Screens & Wires Monitors

Proceedings of IBIC2012, Tsukuba, Japan

THCB02

Table 2: European XFEL Wire Scanner SpecificationsParameter

ValueStroke
Measurement duration
Scanning modes
Motor to beam sync
Position accuracy in a cycle
Width accuracy per cycle
Wire positioning error
Number of wires per fork
Wire material
Fork gap
Wire-wire distance

53mm
5 sec / 4 scanners
Fast (1m/s), Slow
< 1µsec (RMS)
2 µm (RMS)
2 % (RMS)
1 µm
3 + 2 ( 3x90o, ±60o)
Tungsten
15mm
5mm ( 90o )Figure 6: Linear motor parameters recorded during astroke: position(mm, red), velocity(m/s, blue), current (A,green), demand and actual velocity difference (m/s, brown)

Figure 5: XFEL wire scanners’ test setup

tion system reference mark traversing time. Measurement
results for many forward and backward strokes are summarized in Fig. 7. Distributions show time jitter below
1µsec which, in our case of 1m/sec velocity, is equivalent to a sub-micrometer mechanical jitter. This could also
be quoted as a repeatability of the tested linear motor withfine position feedback and triggering systems.

DISCUSSION
achieved. During the test mechanical design and construction precision has been justified while linear motors havedemonstrated reliable performance. To verify motor’s dynamic behavior we have recorded essential parameters during nominal strokes. An example is shown on Fig. 6 where
together with position and velocity also the motor’s current and velocity deviation are displayed for a fast (1m/s)
scanning stroke. An important issue for the XFEL wire
profilers and fast scans in general is mechanical jitter magnitude for triggered scans. We have investigated this byrecording time intervals between the trigger and fine posi-

In the last section we have demonstrated an outstanding
performance of contemporary linear motors as wire scanner drivers. We have proposed to use linear-rotary motorwith attached key-bit wire card as 2-D twisting wire scanner. Estimated planes of possible oscillations of the keybit wires differ from critical planes in 45 deg forks whichshould cure associated vibrational problems reported atLCLS and other centers. This will become possible mainly
due to different alignment of the scanning wires relative todriver unit. In addition the vibrations are normally dumped
along the motion direction.

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3c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Figure 4: Designed horizontal and vertical wire scanners
mounted on vacuum chamber.

THCB02

Proceedings of IBIC2012, Tsukuba, Japan

Rising Edge Events

LinMot Fine Triggering sync-v02 Accuracy
Mean
RMS

60

0.2213E-01
0.304940-1-0.5

00.5

1

1.5

Falling Edge Events

Tref - Ttrigg - 35.97 [µs]MeanRMS400.3300E-01
0.39983010-1-0.5

00.5

11.5

Tref - Ttrigg - 40.44 [µs]c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○[1] K. Wittenburg, “Overview of recent halo diagnosis and nondestructive beam profile monitoring,” Conf. Proc. 39th ICFA
Advanced Beam Dynamics Workshop on High Intensity High
Brightness Hadron Beams 2006 (HB2006)[2] C. Fischer, G. Burtin, R. Colchester, B. Halvarsson, R. Jungand J. M. Vouillot, “Studies Of Fast Wire Scanners For Lep,”Conf. Proc. C 880607, 1081 (1988).
[3] H. Loos, R. Akre, A. Brachmann, R. Coffee, F. -J. Decker,
Y. Ding, D. Dowell and S. Edstrom et al., “OperationalPerformance of LCLS Beam Instrumentation,” SLAC-PUB14121.

200-1.5

We are thankful to S. Vilcins-Czvitkovits, J. Kruse,
A. Ziegler and M. Drewitsch for participation in preparation and running of the XFEL wire scanners’ first prototyping test.

REFERENCES

200-1.5

ACKNOWLEDGMENT

Figure 7: Motor triggering mechanical jitter distribution forthe forward (upper plot) and backward (lower plot) strokes.
Superimposed are shown fitting gaussian functions withdisplayed RMS (one sigma) values.
An apparent difficulty for twisting wire scanner development is the linear-rotary motion transfer into the vacuum
chamber where the key-bit card should operate. For thatone should combine linear bellows with either wobble [7]or torsional [8] bellows.

[4] J. Frisch, R. Akre, F. J. Decker, Y. Ding, D. Dowell, P. Emma,
S. Gilevich and G. Hays et al., SLAC-REPRINT-2012-018.
[5] N. Iida, T. Suwada, Y. Funakoshi, T. Kawamoto andM. Kikuchi, “A method for measuring vibrations in wire
scanner beam profile monitors,” Conf. Proc. C 9803233, 546(1998).
[6] http://www.LinMot.com[7] J. Bosser, J. Camas, L. Evans, G. Ferioli, R. Hopkins, J. Mannand O. Olsen, “Transverse Emittance Measurement With A
Rapid Wire Scanner At The Cern Sps,” Nucl. Instrum. Meth.
A 235, 475 (1985).
[8] Producer: Tru-Flex LLC, http://www.tru-flex.com/ Animation: http://www.youtube.com/watch?v=C3WTtMCU3lE

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