1. reporter: Erk JENSEN/CERN
Report from Parallel Session IIa Energy efficiency/recovery/optimization
reporter: Erk JENSEN/CERN

2. Session IIa, Fri. 8:30 – 10:30 Energy efficiency/recovery/optimization
Mike Seidel (PSI)
Energy efficient technologies for accelerators – an EuCARD-2 effort
Michele Modena (CERN)
Advancements and perspectives on compact and low consumption magnet design for future accelerators
Carlos A. Martins (ESS)
High efficiency pulsed power converters for the ESS accelerator

3. Energy efficient technologies for accelerators – EuCARD 2
Mike Seidel (PSI)

4. Network Acvitity EnEfficient, Eucard-2
EnEfficient: WP3, networking activity to stimulate developments, support accelerator projects, thesis studies etc.
task 1: energy recovery from cooling circuits, Th.Parker, A.Lundmark (ESS) task 2: higher electronic efficiency RF power generation, E.Jensen (CERN) task 3: short term energy storage systems, R.Gehring (KIT) task 4: virtual power plant, J.Stadlmann (GSI) task 5: beam transfer channels with low power consumption, P.Spiller (GSI)
links to all workshops on
Mike Seidel (PSI): Energy efficient technologies for accelerators

5. Example: PSI Facility, 10MW
n: per beamline:
10eV ≈ 20µW
neutrons
public grid ca. 10MW
RF Systems 4.1MW
Beam on targets
1.3MW
muons
+: per beamline
30MeV/c
≈ 300µW
optimization includes not only the accelerator, but also
secondary radiation conversion efficiency
secondary radiation transport and brightness at experiment
signal to noise ratio
instrument efficiency
an overall optimization should be done.
Magnets
 2.6MW
aux.Systems
Instruments
 3.3MW
applies to many facilities:
light source, FEL
n, µ,  source
particle collider
heat  to river, to air
cryogenics
Mike Seidel (PSI): Energy efficient technologies for accelerators

6. Heat Recovery Workshop, Lund, March 2014 [Th.Parker, E.Lindström, ESS]
Participants (Experts) from
DESY, ALBA, SOLEIL, ESS, MAX-4, PSI, DAFNE, ISIS (institutes)
E.ON, Kraftringen, Lund municipality (industry, local authorities)
lab survey on consumption and heat recovery
heat recovery works for many facilities; high temperatures beneficial
local heat distribution system required
greenhouses present interesting application (non-linear scaling)
new facilities MAX-4 and ESS foresee heat recovery on large scale
talks:
Mike Seidel (PSI): Energy efficient technologies for accelerators

7. Efficient RF Generation and Beam Acceleration
RF generation efficiency is key for many accelerator applications, especially high intensity machines
topics at workshop:
klystron development
multi beam IOT (ESS)
magnetrons
high Q s.c. cavities
CPI: multi-beam IOT
E2V: magnetron
THALES: multi-beam klystron
workshop EnEfficient RF sources:
SIEMENS: solid state amplifier
THALES: TETRODE
Mike Seidel (PSI): Energy efficient technologies for accelerators

8. Energy Management strong variations of supply by wind and sun energy
even today strong variation by varying load on grid
 consider „dynamic operation“ of accelerators, depending on supply situation (challenging, loss of efficiency)
 consider options to store energy on site (expensive, evolving technology)
 economy depends on supply volatility and cost of energy
Germany
Mike Seidel (PSI): Energy efficient technologies for accelerators

9. Outlook: workshop in Feb/16, PSI
Proton Drivers with high intensity
for Neutron, Muon, Neutrino production
workshop: comprehensive consideration of efficiency from Grid to secondary beam at experiment/application
topics:
beam intensity demand for particle physics, structure of matter physics
target efficiency, conversion to secondary radiation
accelerator concepts, RF sources + accelerating structures
typical aux. systems, cryogenics, conventional cooling
Mike Seidel (PSI): Energy efficient technologies for accelerators

10. A new Eucard program is planned for 2017-21
Summary
With scarcity of resources and climate change Energy Efficiency becomes important for accelerator projects
Eucard-2/EnEfficient studies heat recovery, RF systems, cavities, magnets, E management
A new Eucard program is planned for
Links to all activities:
Mike Seidel (PSI): Energy efficient technologies for accelerators

11. Advancement and Perspectives of Compact and Low Consumption magnet design
Michele Modena (CERN)

19. High efficiency pulsed power converters for the ESS accelerator Two examples reported: 1) Pulsed klystron modulators 2) Pulsed quadrupole magnets Carlos Martins European Spallation Source Davide Castronovo, Roberto Visintini Elettra Sincrotrone Trieste

20. ESS Klystron modulator – Stacked Multi-Level
(SML) topology
Improved efficiency (~92%), due to minimal number of conversion stages;
Good AC grid power quality (constant power absorption = flicker-free operation, sinusoidal current absorption, unitary power factor);
3.5ms pulse
Magenta: HV output pulse;
Yellow: LV input voltage;
Green: LV input current
Idea: option to integrate PV – Skåne: 60% of Sahara
Pulse (1kV)
AC line voltage
AC line current
Unitary power factor;
Sinusoidal line current, constant amplitude -> No flicker
A yearly energy of 3.4 MW-Year could be collected from such a field. ≈ 1/3 of total

21. Magnets & PC System Optimization
Linac Warm Units (LWU) and M&PC
“Single Pass Machine”  is “DC mode” really needed?
Is “Pulsed Mode” a feasible alternative?
Advantages? Disadvantages?
Magnets and their associated PC are the two sides of a system
Optimization involves magnets AND power converters together
DC vs. Pulsed
Complexity/costs vs. simplification/spares
Let’s consider the Linac Warm Units of ESS.
The accelerator is a single pass one. Particles are emitted at 14 Hz rate, therefore, is DC mode really needed?
The consequence is to verify if a “pulsed solution” is possible and which are the constraints on the pulse shape and period.
And, from this considerations analyse and compare pros and cons.
Quite obvious, indeed.
For the specific case, magnets and power converters are the two halves of a single system. Any optimization process – technical and economical – involve both at the same time.
DC and pulsed modes act in opposition on magnets and power converters. DC mode bring some complications with the magnets, for example the water cooling and simplify the structure of the power converters. Conversely the pulsed mode could simplify the magnets (e.g. air cooling) and complicate the power converters.
Optimization is a matter of weighting the complexity and costs increase on one dish with the simplification and the economical and maintenance spares on the other.

22. Operating Mode, Cooling
LWU* Magnets and Power Converters
Magnet Type
Description
Operating Mode, Cooling
Quantity
N. of PC Q5
Quadrupole magnet
Pulsed, Air-cooled 26 C5
Dual-plane corrector magnet
DC, Air-cooled 13 Q6 95 C6 55
110 Q7 12 D1
Vertical dipole magnet
DC, Water-cooled 2 1 Q8 6 C8 4 8
This is the list of magnets in the LWU.
The quadrupole types Q5, Q6 and Q7 are the more numerous and are involved in the study while the others can be DC.
*LWU = Linac Warm Unit
90% of the ESS accelerator quadrupole magnets changed from DC to pulsed

23. Possible pulse waveform
The transit time of the particle beam is 2.86 ms every 71.4 ms
→ a 4 ms-long flat-top is sufficient
For the pulsed excitation, the following waveform has been considered:
Trapezoidal, 4.5 ms rise/fall, 4 ms flat-top, 14 Hz repetition rate (71.4 ms period)
Current Pulse [4.5 – 4 – 4.5] ms
Here it is the studied waveform. We extended the study also to a little more relaxed one, 8 ms of rise time instead of 4.5 ms. We will explain the reason for this later.

24. Q6 Magnet: DC vs. Pulsed (Air Cooled)
Turns per pole = 24
= 435A
= 137A
PMag = 0.21kW
LMag = 8.2 mH
VPK = 0.79 kV
Pulsed (*) DC
Turns per pole = 78
= 134 A
= 134 A
PMag = 2.62 kW
VMAX = 20 V Q6
3D model of
Q6 quad, pulsed
Taking into account the two most interesting solutions for both Q6 and Q7 (DC means water-cooled), we evaluate here the differences among the models.
It is clear how the pulsed solution has a very low power consumption compared to the DC one.
While Q6 peak voltage in the pulsed case is well below 1 kV, Q7 is very closed to this limit.
In order to reduce the peak voltage, a possible solution is to relax the pulse, increasing the rise and fall times.
In this way, since we are less sensitive to magnet inductance, it is possible to increase for both models the number of turns: the required gradient is obtained with a lower peak current
(*) Rise time 4.5 ms,
flat top time 4 ms and fall time 4.5 ms
Electrical energy consumption of pulsed magnets reduced by a factor of 10 wrt DC magnets

25. Conclusions ●○
Compared several design for magnets Q6 and Q7, both in DC and Pulsed
DC is a standard, well-known solution:
Power consumption  2.4 kW for each QC6; 3.5 kW for each QC7
Water cooling of magnets  de-ionized water plant,…
“Low Power” but stable power supplies (~5 kW)
Pulsed excitation is a less common solution:
Power consumption  significantly more efficient than DC
Air cooling of magnets  no piping, etc. but heat to environment
High peak output voltage  risk of exceeding 1 kV (design & operations)
Shape of the pulse is important (e.g. rise time: 8.0 ms vs. 4.5 ms)
The total cost of pulsed magnets are slightly lower than of DC magnets
Our conclusions can be summarized as follow.
Adopting the DC solution, means following a well known standard, at the cost of significantly higher power dissipation in the magnets and the need of water cooling with the drawbacks I’ve just mention.
The power supplies are low power ones but require a stability higher than commercial standard.
The pulsed excitation is a less common solution that brings some remarkable positive effects, in terms of power consumption and air cooling requirements.
For this, one has to take into account higher peak voltages and pay attention on the shape of the pulse. Since these issues are controllable I’ve not marked them as real drawbacks.