%Cryogenic Systems

\section{Introduction}

In order to apply bulk refrigeration to accelerator components, the
cooling requirements for each device need careful consideration.  The
specification and application of bulk refrigeration will naturally
follow a thorough investigation and careful engineering of cooled
components.  It is this study that sets the stage for making the
connection between the cooling requirements and the refrigeration
system cooling arrangement and hardware.  For our case, the cooled
devices are rf cavities, superconducting magnets, and hydrogen
absorbers, all of which are well characterized in terms of heat loads.


\section{Cooled Components}

The Neutrino Factory uses cryogenic cooling in all of its major
sections. A general listing of the
cryogenic cooling needs are: 
\begin{itemize} 
\item The proton driver, which has a 
superconducting linac (SCL) made of three sections, each with
its own energy range and cavity cryostat arrangement, and all operating at 2 K.
\item The target
station and pion capture system, which utilize 1.9 K and 4.4 K
refrigeration for the superconducting capture solenoids.  
\item The
decay channel, which has superconducting
magnets operating at 4.4 K.  
\item The phase rotation section, which uses superconducting solenoids that
operate at 4.4 K.
\item The mini-cooling section, which has solenoids operating at 4.4 K and two-phase hydrogen absorbers operating at 16-19~K. 
\item The bunching and cooling channel, which
has superconducting solenoids operating at 4.4 K
and 2.5 K, as well as liquid-hydrogen absorbers operating at 16-19 K. 
\item The linear accelerator
section, which has superconducting rf cavities operating at 2.5 K and solenoids operating at 4.4~K. 
\item The recirculating linear accelerator, which again has rf 
cavities operating at 2.5 K and superconducting magnets operating at 4.4 K.
\item The storage ring, which has superconducting dipoles and quadrupoles operating at 4.4 K.
\end{itemize}
  All the superconducting
magnets and superconducting rf cavities also require cooling in the
5-8 K and 50-80 K range for shields and current leads.  Cryogenic
cooling, regardless of temperature, is accomplished via helium
refrigeration.

Large helium refrigerators are envisioned here,  because they naturally
provide all temperature ranges required, and typically provide a
higher Carnot efficiency than do smaller units.  Larger refrigerators, 
typically with turbine 
expanders, also offer enhanced cooling capacity at higher
temperatures, as well as options to improve the cool-down and
liquefaction processes with the addition of liquid nitrogen.  The
requirements of superconducting magnets, absorbers, and
rf cavities will define the interface between refrigeration and cooled devices.

In the muon cooling channel and the phase rotation channel, a 16 K
stream cools the magnet shields and leads as well as the liquid-hydrogen 
absorbers. Figure~\ref{CRYO:fg1} shows the cooling circuit to a typical coupling (``B'') coil in the muon cooling channel. The same type of flow
circuit can be applied to the solenoids in the phase rotation section.
\begin{figure}
\begin{center}
\includegraphics[width=4in]{../template/report/ps-and-eps/iarocci-fg1.eps}
\caption[Magnet helium cooling circuit for the (``B'') coils]{The magnet helium cooling circuit for a typical coupling (``B'') coil in the cooling section.}
\label{CRYO:fg1}
\end{center}
\end{figure}
The focusing (``A") coils in the cooling channel have liquid-hydrogen
absorbers within them. The cryostat for the liquid-hydrogen
absorber is a part of the magnet cryostat. The 2.75-m-long cell
 focusing magnets operate at 4.4 K, whereas helium delivered to the hydrogen
absorber enters at about 16 K and leaves at about 18 K.  Helium entering the absorber heat exchanger must
remove about 330 W of heat from the liquid-hydrogen absorber when the
full intensity muon beam is present. When there is no beam,
the heat into the 16 K helium flow circuit is reduced to about 55 W.  
Figure~\ref{CRYO:fg2} shows a helium flow circuit for the focusing coil and liquid-hydrogen absorber in a 2.75~m cooling cell. As seen in both Figs.~\ref{CRYO:fg1} and ~\ref{CRYO:fg2}, the
shields and leads are cooled from the 16 K helium circuit. Shield and
lead gas exits the cryostat at 300 K. The corresponding 16 K cooling requirement for
the 1.65~m cell hydrogen-absorbers are 150~W with the muon beam
on, and 40~W with the beam off.
\begin{figure}
\begin{center}
%\includegraphics[bb=0 300 479 659,width=4in,clip]{iarocci-fg2.eps}
\includegraphics[width=4in,clip]{../template/report/ps-and-eps/Refer_Fig_3.eps}
\caption[Magnet helium cooling circuit for the (``A'') coil in a 2.75~m cell]{The magnet helium cooling circuit for a typical focusing (``A'') coil and the liquid-hydrogen absorber in the 2.75-m cooling cell.}
\label{CRYO:fg2}
\end{center}
\end{figure}

The focusing coils in the 1.65-m cooling cell have a peak
induction in the winding of 8.5~T.  In order for these coils to be
made from Nb-Ti, they must operate at a reduced temperature
(between 2.5 and 3.0 K). The heat load into the (``A'') coils comes from
the cold-mass supports and from thermal radiation from the shield; 
 there is almost no heating due to muon decay or AC losses in the
superconductor. By using the 4.4 K stream to intercept heat from
the cold-mass supports, shield, and leads, the heat leak into the focusing coil  can be reduced from 1.8 W to about 0.3 W.

A low heat load at 2.5 K can be removed by using a small 2 K cooling
circuit that operates off of the 4.4 K refrigeration circuit. The
cooling circuit consists of a heat exchanger that takes liquid helium
from the two-phase flow circuit. After passing through the
high-pressure side of the heat exchanger, the liquid helium is
throttled through an expansion valve down to a pressure of about 40~ton.  
The helium is now two-phase helium at 2.2 K, with evaporation
cooling of the load. The low-pressure gas phase passes through
the low-pressure side of the heat exchanger and is finally returned to the
refrigerator compressor at 300 K.  To generate 0.3 W of cooling at 2.2
to 2.5 K, a helium flow rate of 0.015~g/s is needed. Since
this helium is returned to the refrigerator warm, it is equivalent to
helium liquefaction. The liquefaction of 0.015~g/s of helium
corresponds to about 1.5 W of refrigeration at 4.4 K.  Figure~\ref{CRYO:fg3}
shows the helium cooling circuit for a 1.65-m cooling cell (``A'') coil and its hydrogen absorber.
\begin{figure}
\begin{center}
\includegraphics[width=4in]{../template/report/ps-and-eps/iarocci-fg3.eps}
\caption[Helium cooling circuit for the (``A'') coils in a 1.65~m cell ]{A helium cooling circuit for the focusing coils and the liquid-hydrogen absorber in the 1.65-m cooling cell.}
\label{CRYO:fg3}
\end{center}
\end{figure}     

\section{Component Loads}
The estimated refrigeration requirements for each cooled device,
including the primary static (ambient) and dynamic (beam heating)
higher temperature secondary or shield loads, and anticipated cooling
arrangement (thermodynamic state) have been considered for the entire
accelerator.  To ease the evaluation of refrigeration component
requirements, the given loads at various state points are all expressed as
an equivalent load at 4.5 K.  This approach gives a better feel for
the refrigeration equipment, and hence a means of comparison with
other installations in terms of size, capital cost, and operational
demands.  Considerations for reliability, helium plant economics
(including standard refrigeration availability), installation costs,
operation costs and difficulty, are all folded into specifying
refrigerators, and in the end will define their sizes and
number.

For each group of accelerator components, (see Fig.~\ref{CRYO:fg4} for the
approximate location of each group), Table~\ref{CRYO:tb1} shows the integrated
primary heat load and thermodynamic state, the secondary heat load and
state, and the equivalent loads normalized to 4.5 K.  The table
follows the accelerator layout, starting at the source and
working toward the muon storage ring.  The equivalent load at 4.5 K is
estimated by multiplying the primary load by the ratio of ideal work at the primary load condition to the equivalent ideal work at 4.5 K.  The ideal work is found from Carnot's formula, $\frac{(T_a-2.5)}{2.5}/\frac{(T_a-4.5)}{4.5}\approx 1.8.$ for the 2.5 K condition.  The
temperature $T_a$ is taken as  300 K.  The loads summarized in 
Table~\ref{CRYO:tb1a}, are in terms of base-load at 4.5 K
equivalent, and base-load-equivalent with 30\% contingency added.  The
percentage of total equivalent load at 4.5 K for the primary and/or
the secondary load is also shown to give an understanding of  the areas of
refrigeration concentration, and give a feeling for the relative size
requirements.


The last two columns, equivalent primary and equivalent secondary
loads, from Table~\ref{CRYO:tb1a}, are combined to give a summary of the total 4.5 K
equivalent loads and equivalent 4.5 K loads with 30\% contingency.  These
values are shown in Table~\ref{CRYO:tb2}.  It is from this table that a preliminary refrigerator sizing has been made.
\begin{figure}
\begin{center}
\includegraphics[width=0.9\linewidth]{../template/report/ps-and-eps/iarocci-fg4.eps}
\caption{Site layout.}
\label{CRYO:fg4}
\end{center}
\end{figure}

\section{Refrigeration Selection}
%\begin{table}[!htb]
From Table~\ref{CRYO:tb2} and the accelerator layout an assessment of
the number and size  of refrigerators, and possible locations is
possible.  This is reflected in Fig.~\ref{CRYO:fg4}.  Based upon our 
understanding of large refrigeration systems applied to
accelerators, the choice for this application is to use a
few large 4.5 K refrigerators.  The low temperature ($< 4.5$~K) areas
are covered using low temperature cold boxes, with cold pumps,
tied into the local 4.5 K refrigerator.  This design approach  
minimizes the distance between the load and the cooling system that requires sub-cooling and sub-atmospheric cold pumps.  The benefit is a linear reduction
of large diameter pumping lines required for this application.
Large diameter vacuum insulated transfer lines are very 
expensive, so minimizing here is prudent.  Table~\ref{CRYO:tb2} gives a feeling for the location of these sub-cooling cold boxes, and 
 also suggests ways to  isolate and/or group component loads with proximity
and capacity considered.  A way of coalescing loads by location
is shown in Table~\ref{CRYO:tb3}.

With reference to Table~\ref{CRYO:tb3}, inclusive of contingency, area
specific loads at locations (``A''), (``B''), and (``C'') could be divided into two
4.5 K refrigerators, for each location, of the approximate capacity of
the machines in operation at the Relativistic Heavy Ion Collider at
BNL~\cite{CRYO:ref1},~\cite{CRYO:ref2}, those previously used for the LEP Electron--Positron Collider at CERN~\cite{CRYO:ref3}, ot the new
refrigerators under construction for LHC project~\cite{CRYO:ref4},~\cite{CRYO:ref5},~\cite{CRYO:ref6}.  For
purposes of system design here, the 18 kW machines under construction for
the LHC are used.  Systems of similar size are encountered
 also in operation at CEBAF (Jefferson Laboratory)~\cite{CRYO:ref7}. The
feasibility of installing refrigerators of the sizes indicated above
has certainly been demonstrated at many places.

Integrating local accelerator heat loads into one or more large
refrigerators is cost effective in terms of initial capital
investment, because it eliminates much of the duplication associated
with building many smaller capacity refrigerators.  Installation and
operation follow the same philosophy.  To support the accelerator
loads other than 4.5 K, the refrigerators will incorporate process
supply and return passes to meet the higher temperature requirements
of items such as the shields and absorbers.  These secondary loads,
shown in Table~\ref{CRYO:tb1}, are typical and would be specified as part of a
refrigerator procurement.  In essence, each refrigerator will supply
the 4.5 K for direct application and all higher temperature needs.
Also, each refrigerator will provide the necessary refrigeration for
the lower temperature cold boxes.  Table~\ref{CRYO:tb1a} summarizes 
the actual loads at operating temperatures below 4.5 K.  


To produce temperatures below the temperature range of the 4.5 K
refrigerators, stand-alone cold boxes, containing at least one heat
exchanger and a series of cold compressors are used.  The
production of 1.9 and 2.5 K cooling, requires pumping on saturated liquid helium
to a pressure of 16 or 100 mbar, respectively.  The pumping scheme is
usually optimized when located as close as possible to the cooled device, so that transfer line hydraulic losses are minimized.  This
approach also minimizes cost, because low-pressure process pipes,
connecting the pumps to accelerator components, are typically much
larger diameter (possibly a factor of 4) and therefore more expensive
to build than the transfer lines that connect the refrigerator to the
low-temperature cold boxes.  The actual cold pumps, located within the
local cold box, can achieve the desired pressure with a series
arrangement, usually 4 or 5 stages being required, or some pumping can
be accomplished at room temperature with warm compressors, which
reduces the number of cold stages to 3.  

\section{Capital Cost, Installation, and Operation}
\subsection{Capital Cost}

The components that drive the capital cost of large cryogenic
refrigeration systems, in descending order of relative cost, are:
\begin{itemize}
\item the 4.5 K refrigeration and associated warm compressor system, reduced
temperature cold boxes and cold compressors
\item transfer piping 
\item process
distribution control or valve boxes
\item cold and warm helium recovery
\item storage volumes and controls.
\end{itemize}
 Building and
utility requirements are considered elsewhere (see Chapter~\ref{CHAP:conventional}); here we consider the components
associated with refrigeration to the ends of each interface to each cooled
device.  The component installation and interface costs are specific to each 
 cooled item.  From experience with the
construction of RHIC, the cost for installation materials and labor,
in terms of percentage of capital cost, in descending order, comes from:
transfer piping, refrigeration, valve boxes, reduced temperature cold
boxes, controls, and helium recovery/storage.  
%Tables~\ref{CRYO:tb4a} and ~\ref{CRYO:tb4b} summarize the required cryogenic equipment and its estimated capital and installation costs.

Estimates for cryogenic transfer piping length are based upon the
length of the particular device, which were considered as a unit (see Table~\ref{CRYO:tb3}) and integrated into one 4.5 K refrigeration plant.  In the case of the
recirculating linac the perimeter is used, and for the storage ring,
with its simpler cooling requirement, the end-to-end length is chosen.
A small contingency length is added to these values to allow for
connection to the refrigerator (and cold boxes if they are needed).  
%The transfer piping length is shown in Table~\ref{CRYO:tb4b}, in the \textsl{Refrigeration Component/ Service} column.  Installation costs, including support
% stands, rigging, field interconnection, leak and pressure testing,
%etc., range from a factor of 2 to a value equal to the capital cost of the transfer piping,
%depending upon location.  The tilted storage ring will naturally be a
%more difficult installation task.

\section{Operational Issues}
\subsection{Power, Operations Labor, Maintenance}
The operating cost, mainly electrical power, is tied directly to the
cycle efficiency.  This subject has been addressed in detail for the
18~kW machines at CERN~\cite{CRYO:ref5},~\cite{CRYO:ref6} with the present efficiency at about 30\%
Carnot, yielding a figure of merit (W$_{in}$/ W$_{ref}$, 4.5 K) of 250.  For our case, the refrigeration with full contingency, 105 kW, corresponds to 
$\approx 26$~MW of electrical power.  Under normal operating conditions,
estimated at 81 kW, the electrical power required is 20 MW.  
%See Table~\ref{CRYO:tb4c} cost summary for costs associated with operation.

The labor required to operate a facility of this nature could be
derived from the models developed and used at RHIC (BNL), CEBAF
(Jefferson Laboratory), or LEP (CERN).  For this part of the study, 
the RHIC facility is used as the model and the operation of LEP is
referenced.  Information gathered from these operating facilities is
used to project the needs for the present study.  The same approach is used
for maintenance of refrigeration systems.  The operation of the four
18~kW plants at LEP involves a group of 37~people, the direct
operation and maintenance of the refrigerators is accomplished by 15
persons.  Operation of cryogenic systems at BNL includes, RHIC, with its
refrigerator and warm compressors, instrumentation and controls, and
ring process equipment, g--2, and experimental programs that require
cryogenics.  The manpower dedicated to the operation of the RHIC
refrigerator directly, is on the average higher than at LEP.  
%The projected manpower for purposes of this study is shown in the summary of Table~\ref{CRYO:tb4c}.


\subsection{Cryogenic Safety}

It is of prime importance to consider safety as a criterion when
providing refrigeration of this magnitude within the confinement of
building structures.  Careful attention must be paid to providing an
effective means of access and egress for this facility, with its long
linear dimensions, because of the possibility of an inadvertent
release of cryogen at a high volumetric flow rate under certain fault
scenarios.  The installation and testing experience gained at RHIC,
with reference to work accomplished at the SSC, FNAL, and CEBAF, has
shown the prudent approach revolves around good cryogenic component
design, governed by conformance to ASME pressure vessel code
requirements and strict attention to the minimization of ``ODH'' (Oxygen
Deficiency Hazard) risks.  This would be accomplished by designing
building ventilation systems to ensure the safest ODH class.  These
ODH classes range from 0 to 4, and in our case class A0 is selected.
\clearpage
%\begin{table}[!htb]
%\newcommand{\PreserveBackslash}[1]{\let\temp=\\#1\let\\=\temp}
%\let\PBS=\PreserveBackslash %shorthand
\begin{center}
\tablecaption{Devices and heat loads.}
\label{CRYO:tb1}
\tablefirsthead{%
\hline
\multicolumn{1}{|p{3cm}}{{\small Primary Temperature/ State/ Primary Load at State}} &
\multicolumn{1}{|p{3cm}}{{\small Cryogenic Secondary (Shield) Load/ State}} & 
\multicolumn{1}{|p{3cm}}{{\small Approximate Equivalent Primary Load at 4.5 K/ \% Total Primary Load Equivalent}}&
\multicolumn{1}{|p{3cm}|}{{\small Approximate Equivalent Secondary Load at 4.5 K/ \% Total Secondary Load Equivalent}} & \\
\hline}
\tablehead{%
\hline
\multicolumn{5}{|c|}{{\small continued from previous page}}\\
%\hline
%\multicolumn{1}{|p{3.5cm}}{\small Primary Temperature/ State/ Primary Load at State} &
%\multicolumn{1}{|p{3.5cm}}{\small Cryogenic Secondary (Shield) Load/ State} & 
%\multicolumn{1}{|p{3.5cm}}{\small Approximate Equivalent Primary Load at 4.5 K/ \% Total Primary Load Equivalent}&
%\multicolumn{1}{|p{3.5cm}|}{\small Approximate Equivalent Secondary Load at 4.5 K/ \% Total Secondary Load Equivalent} & \\
\hline
\multicolumn{1}{|p{3cm}}{{\small Primary Temperature/ State/ Primary Load at State}} &
\multicolumn{1}{|p{3cm}}{{\small Cryogenic Secondary (Shield) Load/ State}} & 
\multicolumn{1}{|p{3cm}}{{\small Approximate Equivalent Primary Load at 4.5 K/ \% Total Primary Load Equivalent}}&
\multicolumn{1}{|p{3cm}|}{{\small Approximate Equivalent Secondary Load at 4.5 K/ \% Total Secondary Load Equivalent}} & \\
\hline}
\tabletail{%
\hline
\multicolumn{5}{|c|}{{\small continued on next page}}\\
\hline}
\tablelasttail{\hline}
\begin{supertabular}{|p{3cm}|p{3cm}|p{3cm}|p{3cm}|p{2cm}|}
%\begin{supertabular} {|>{\PBS\raggedleft\hspace{0pt}}p{3cm}%|c|c|c|c|}
%|>{\PBS\raggedleft\hspace{0pt}}p{3cm}%
%|>{\PBS\raggedleft\hspace{0pt}}p{3cm}%
%|>{\PBS\raggedleft\hspace{0pt}}p{3cm}%
%|>{\PBS\raggedleft\hspace{0pt}}p{2cm}|}
\multicolumn{5}{|c|}{{\small SC Linac rf Cavities / 100 m}}\\
\hline
{\small 2.5 K/ 2 Phase/ 7.1 kW }&
{\small 8.3 kW/ (5--8 K) 87 kW/ (40--60 K)}&
{\small 12.8 kW/ 21\% }& 
{\small 8 kW (5--8 K) 8.7 kW (40--60K)/49.7\% }& \\
\hline
\multicolumn{5}{|c|}{{\small Matching Solenoids (Capture) / 10 m}}\\
\hline
{\small 1.9 K/ 2 Phase/6.3 kW }&
{\small 0.82 kW/ (30--300)}&
{\small 14.8 kW/ 24\%}&
{\small 0.3 kW/0.9\%}&
{\small beam loading}\\
\hline
\multicolumn{5}{|c|}{{\small IL1 / 110 m}}\\
\hline
{\small 4.4 K/ 2 Phase/ 0.55 kW }&
{\small 0.59 kW/ (40--60 K)}&
{\small 0.55 kW/ 0.9\%}&
{\small 0.06 kW/ 0 .18\% }&
{\small 4.5 K load = 5 W/m}\\
\hline
\multicolumn{5}{|c|}{{\small Minicooling / 5 m}}\\
\hline
{\small 16 K/ 2 Phase/  5.5 kW}&
&
{\small 1.5 kW/ 2.4\%}&
& \\
\hline
\multicolumn{5}{|c|}{{\small IL2 and IL3 / 190 m}}\\
\hline
{\small 4.4 K/ 2 Phase/ 0.09 kW}&
{\small 1.0 kW/ (40--60 K)}&
{\small 0.09 kW/ 0.15\%}&
{\small 0.1 kW/ 0.3\%} &
{\small 4.5 K load =
0.47~W/m }\\
\hline
\multicolumn{5}{|c|}{{\small Matching and  Bunching Solenoids / 50 m}}\\
\hline
{\small 4.4 K/ 2 Phase/ 
0.27 kW}&
{\small 3.0 kW (16--40 K)}& 
{\small 0.27 kW/ 0.44\% }&
{\small 0.8 kW/ 2.4\%}& \\
\hline 
\multicolumn{5}{|c|}{{\small Cooling/ 100 m}}\\
\hline
{\small 16 K/ 2 Phase/ 10.6 kW}&
&
{\small 2.9 kW/ 4.7\% }&
& \\
\hline
\multicolumn{5}{|c|}{{\small Acceleration Linac (11 short, 16 intermediate, 19 long cells) / 250 m}}\\
\hline
{\small 2.5 K/ 2 Phase/ 
1.86 kW }&
{\small 2.2 kW (5--8 K) 
22 kW (40--60 K)}& 
{\small 3.37 kW/ 5.5\%}&
{\small 2.0 kW (5--8 K) 
2.2 kW (40--60 K)/
12.5 \%}& \\ 
\hline
\multicolumn{5}{|c|}{{\small Recirculating Linac (48 long cells) / 300 m}}\\
\hline
{\small 2.5 K/ 2 Phase/ 
4.7 kW}&
{\small 5.57 kW (5--8 K) 55.7 kW (40--60 K)}&
{\small 8.5 kW/ 13.8\%}&
{\small 5 kW (5--8 K)
5.6 kW (40--60K)/
31.5 \%}& \\
\hline
\multicolumn{5}{|c|}{{\small Dipole/ Quadrupole Magnets, for Recirculating Linac}}\\
\hline
{\small 4.4 K/ 2 Phase/ 
0.47 kW}&
{\small 6.0 kW/ (40--60 K)}&
{\small 0.47 kW/ 0.76\%}&
{\small 0.6 kW/ 1.8\%}& \\
\hline
\multicolumn{5}{|c|}{{\small Storage ring arcs (53~m $\times 2$ inclined)}}\\
\hline
{\small 4.4 K/ super-critical/ 1.0 kW (static) + 1.0 kW (dynamic)}&
{\small 2.0 kW/ (40--60 K)}&
{\small 2.0 kW (static \& dynamic)/ 3.2\%}&
{\small 0.2 kW/ 0.6\%}&
{\small dynamic beam loading}\\
%\hline
\end{supertabular}
\end{center}
%\end{sidewaystable}
%\end{table}
\clearpage
\begin{table}[!bht]
\begin{center}
\caption{Load summary.}
\label{CRYO:tb1a}
\begin{tabular}{|p{3.5cm}|p{3.5cm}|p{3.5cm}|p{2cm}|p{2cm}|}
\hline
{\small Total}&{\small Primary} & {\small Secondary} & {\small Primary Equivalent} & {\small Secondary Equivalent}\\
\hline
Total (2.5 K, 4.4 K, 
16 K without contingency)&
13.66 kW (2.5 K)
3.38 kW (4.4 K)
16.1 kW (16 K)&&&\\
\hline
Total (5--8 K, 
16--40 K, 40--60 K without contingency)&
&
16.1 kW (5--8 K)
3.0 kW (16--40 K)
124 kW (40--60 k)&&\\
\hline
Total equivalent
( 4.5 K without contingency)&&&
47.4 kW&
33.6 kW\\
\hline
Total equivalent
( 4.5 K with 30\% contingency)&&&
61.6 kW&
43.7 kW\\
\hline
\end{tabular}
\end{center}
%\end{sidewaystable}
\end{table}
%\normalsize
\clearpage
\begin{center}
\tablecaption{Load concentrations and percentages.}
\label{CRYO:tb2}
\tablefirsthead{%
\hline
\multicolumn{1}{|p{3cm}}{{\small Cooled Device}}&
\multicolumn{1}{|p{3cm}}{{\small \% Total and Equivalent 4.5 K Load in kW (Primary Load)}}&
\multicolumn{1}{|p{3cm}}{{\small \% Total and Equivalent 4.5 K Load in kW (Secondary Load)}}&
\multicolumn{1}{|p{3cm}|}{{\small Total Equivalent 4.5 K Refrigeration, Primary plus Secondary in kW/ Total with 30\% Contingency in kW}}\\
\hline}
\tablehead{%
\hline
\multicolumn{4}{|c|}{{\small continued from previous page}}\\
\hline
\multicolumn{1}{|p{3cm}}{{\small Cooled Device}}&
\multicolumn{1}{|p{3cm}}{{\small \% Total and Equivalent 4.5 K Load in kW (Primary Load)}}&
\multicolumn{1}{|p{3cm}}{{\small \% Total and Equivalent 4.5 K Load in kW (Secondary Load)}}&
\multicolumn{1}{|p{3cm}|}{{\small Total Equivalent 4.5 K Refrigeration, Primary plus Secondary in kW/ Total with 30\% Contingency in kW}}\\
\hline}
\tabletail{%
\hline
\multicolumn{4}{|c|}{{\small continued on next page}}\\
\hline}
\tablelasttail{\hline}
\begin{supertabular}{|p{4cm}|p{3.5cm}|p{3.5cm}|p{4cm}|}
SC linac rf cavities&
12.8 kW/ 21\%&
16.7/ 49.7\%&
29.5/ 38.4\\
\hline
Matching solenoids (capture)&
14.8 kW/ 24\%&
0.3 kW/0.9\%&
15.1/ 19.6\\
IL1 (110 m)&
0.55 kW/ 0.9\%&
0.06 kW/ 0.18\%&
0.61/ 0.8\\\hline
Minicooling&
1.5 kW/ 2.4\%&&
1.5/ 1.95\\
IL2 and IL3 (190 m)&
0.09 kW/ 0.15\%&
0.1 kW/ 0.3\%&
0.2/ 0.26\\\hline
Matching and bunching solenoids&
0.27 kW/ 0.44\%&
0.8 kW/ 2.4\%&
1.1/ 1.4\\\hline
Cooling&
2.9 kW/ 4.7\%&&
2.9/ 3.8\\\hline
Acceleration linac (11 short, 16 intermediate, 19 long cells)&
3.37 kW/ 5.5\%&
4.2 kW/ 12.5\% &
7.7/ 10\\\hline
Recirculating linac (48 long cells)&
8.5 kW/ 13.8\%&
10.6 kW/ 31.5\%&
19.1/ 24.8\\\hline
Dipole/ quadrupole magnets, for recirculating linac&
0.47 kW/ 0.76\%&
0.6 kW/ 1.8\%&
1.1/ 1.4\\\hline
Storage ring arcs (53 m x 2 inclined)&
2.0 kW/ 3.2\%&
0.2 kW/ 0.6\%&
2.2/ 2.9\\\hline
\textbf{Total Load}&
47.4&33.6&
81/ 105.3\\
\end{supertabular}
\end{center}
%\end{table}
\clearpage
\begin{table}[!bht]
\begin{center}
\caption{Load concentrations grouped by area, with 30\% contingency.}
\label{CRYO:tb3}
\begin{tabular}{|lc|}
\hline
A- SC linac rf cavities (kW) &                       38.4\\
B- Items 2--7 inclusive, from Table~\ref{CRYO:tb2} (kW) &            27.8\\  
C- Acceleration and recirculating linacs (kW)&       34.8\\
D- Storage ring (kW)                          &        3.0 \\
\hline
\end{tabular}
\end{center}
\end{table}
\begin{thebibliography}{99}
\bibitem{CRYO:ref1}  M. Iarocci, et al., \textsl{RHIC 25 kW Refrigerator and Distribution
System, Construction, Testing, and Initial Operating Experience},
Advances in Cryogenic Engineering, \textbf{Vol. 43}, P. Kittle, Ed., Plenum
Press, New York ( 1997), p 499.

\bibitem{CRYO:ref2}  M. Iarocci, et al., RHIC Accelerator Commissioning, Cryogenic
Tests and Initial Operating Experience of the 25 kW Refrigerator and
Distribution System, Advances in Cryogenic Engineering, \textbf{Vol. 45}, Q-S
Shu, Ed., Plenum Press, New York ( 1999), p 1323.

\bibitem{CRYO:ref3}  N. Bangert, Ph. Gayet, et al., Operation of the Four 12 kW at 4.5
K Refrigerators for LEP, Advances in Cryogenic Engineering, \textbf{Vol. 45},
Q-S Shu, Ed., Plenum Press, New York ( 1999), p 1293.

\bibitem{CRYO:ref4}  S. Claude, et al., Specification of the Four large 4.5 K Helium
Refrigerators for the LHC, Advances in Cryogenic Engineering, 
\textbf{Vol. 45}, Q-S Shu, Ed., Plenum Press, New York ( 1999), p 1269.

\bibitem{CRYO:ref5}  P. Gadget, et al., Two Large 18 kW (Equivalent Power at 4.5 K)
Helium Refrigerators for CERN's LHC Project, Supplied by Air Liquids,
Advances in Cryogenic Engineering, \textbf{Vol. 45}, Q-S Shu, Ed., Plenum
Press, New York ( 1999), p 1277.

\bibitem{CRYO:ref6}  J. Bose, et al., Two Large 18 kW (Equivalent Power at 4.5 K)
Helium Refrigerators for CERN's LHC Project, Supplied by Line
Kryotechnik, Advances in Cryogenic Engineering, \textbf{Vol. 45}, Q-S Shu,
Ed., Plenum Press, New York ( 1999), p 1285.  

\bibitem{CRYO:ref7} C. H. Rode, et al.,
2.0 K CEBAF Cryogenics, Advances in Cryogenic Engineering, \textbf{Vol. 35},
R. W. Fast, Ed., Plenum Press, New York ( 1990), p 275.
\end{thebibliography}
