# RHIC RUN 3 (FY2003) Running Projections 

# Thomas Roser June 28, 2002

This note discusses possible operation modes for the RHIC FY2003 running
period including constraints from cryogenic cool-down, machine set-up
and beam commissioning.

After the summer shut-down both RHIC rings are at room temperature and
many areas have been brought to atmospheric pressure. A full 4 weeks
will be required to cool down to 4 Kelvin. By the end of the run the new
Helium storage system and the Liquid Nitrogen pre-cooler will be
available. In this case only one week of refrigerator operation is
required for the ring warm-up to 80 Kelvin.

A number of RHIC running modes are considered in RHIC, such as Au-Au
collisions, polarized proton collision, deuteron on Au collisions, etc.
At this year's RHIC retreat it was agreed that for each mode we should
plan for 2 weeks of machine set-up with the goal to establish collisions
and a 3-week machine development period ("ramp-up") with the goal of
reaching a "final" luminosity for the subsequent data taking period.
During this ramp-up period detector set-up can occur, however with
priority for machine development. No significant machine development
would by scheduled during the data taking period.

For example, the expected 29 weeks of RHIC refrigerator operation during
FY2003 would be scheduled in the following way for two RHIC operating
modes:

Cool-down: 4 weeks

Set-up mode 1 2 weeks

Ramp-up mode 1 3 weeks

Data taking mode 1 7 weeks

Set-up mode 2 2 weeks

Ramp-up mode 2 3 weeks

Data taking mode 2 7 weeks

Warm-up 1 week

For 3 modes of equal length the data taking period would be 3 weeks per
mode.

Table 1 shows the luminosities achieved at the end of the RUN 2
(FY2001/02) for Au-Au and proton-proton collisions. The average store
luminosity was for a store with no hardware problems and with a
luminosity that agreed well with predicted values from intensity and
beam emittance (store \# 1812 for Au-Au, store \# 2304 for p-p). The
integrated weekly luminosity is the average over the last few weeks
during which the luminosity was fairly constant. The ratio of average
weekly luminosity over store luminosity was 27% and 42% for Au-Au and
p-p, respectively. Note that this includes all interruptions such as
maintenance, studies, etc.

+--------+-------+----------+----+--------+-------+--------+---------+
| Mode   | \#    | Io       | \  | Emi    | L~    | L~a    | L~ave~  |
|        | bu    | ns/bunch | *\ | ttance | peak\ | ve~(st | (week)\ |
|        | nches | \[^9^\]  | \  |        | ~     | ore)~\ | \[wee   |
|        |       |          | [m | \[m\]  | \[cm^ | ~\[c   | k^-1^\] |
|        |       |          | \] |        | -2^s^ | m^-2^s |         |
|        |       |          |    |        | -1^\] | ^-1^\] |         |
+--------+-------+----------+----+--------+-------+--------+---------+
| Au-Au  | 55    | 0.6      | 1  | 15-40  | 3.71  | 1.5    | 24      |
|        |       |          |    |        | 0^26^ | 10^26^ | (b)^-1^ |
+--------+-------+----------+----+--------+-------+--------+---------+
| (p-p)  | 55    | 70       | 3  | 25     | 1.81  | 1.2    | 0.3     |
|        |       |          |    |        | 0^30^ | 10^30^ | (       |
|        |       |          |    |        |       |        | pb)^-1^ |
+--------+-------+----------+----+--------+-------+--------+---------+

Table 1: Achieved beam parameters and luminosities for the RHIC RUN 2
(FY2001/02)

Table 2 lists the expected **maximum** peak and average luminosities for
the possible modes in FY2003 that could be achieved by the end of the
3-week ramp-up period.

For all modes it was assumed that the beam energy is 100 GeV/nucleon.
The average store luminosity is for a "good" store as defined above.
This is a number predictable from the beam parameters. The weekly
integrated luminosity was then obtained by using a ratio of 40% between
average weekly and average store luminosity based on our experience from
p-p running. The expected sigma of the diamond length is 20 cm due to
the availability of the full voltage from the 200 MHz storage cavities.
Note that beta-star of 1 m is only available at PHENIX and STAR. PHOBOS
and BRAHMS are limited to 2m.

+--------+-------+----------+----+--------+-------+--------+---------+
| Mode   | \#    | Io       | \  | Emi    | L~    | L~a    | L~ave~  |
|        | bu    | ns/bunch | *\ | ttance | peak\ | ve~(st | (week)\ |
|        | nches | \[^9^\]  | \  |        | ~     | ore)~\ | \[wee   |
|        |       |          | [m | \[m\]  | \[cm^ | ~\[c   | k^-1^\] |
|        |       |          | \] |        | -2^s^ | m^-2^s |         |
|        |       |          |    |        | -1^\] | ^-1^\] |         |
+--------+-------+----------+----+--------+-------+--------+---------+
| Au-Au  | 56    | 1        | 1  | 15-40  | 141   | 3      | 70      |
|        |       |          |    |        | 0^26^ | 10^26^ | (b)^-1^ |
+--------+-------+----------+----+--------+-------+--------+---------+
| (p-p)  | 112   | 100      | 1  | 25     | 161   | 10     | 2.8(    |
|        |       |          |    |        | 0^30^ | 10^30^ | pb)^-1^ |
+--------+-------+----------+----+--------+-------+--------+---------+
| d-Au   | 56    | 80(d),   | 2  | 20     | 41    | 1.6    | 4       |
|        |       | 1(Au)    |    |        | 0^28^ | 10^28^ | (       |
|        |       |          |    |        |       |        | nb)^-1^ |
+--------+-------+----------+----+--------+-------+--------+---------+
| Si-Si  | 56    | 7        | 1  | 20     | 51    | 2      | 5       |
|        |       |          |    |        | 0^28^ | 10^28^ | (       |
|        |       |          |    |        |       |        | nb)^-1^ |
+--------+-------+----------+----+--------+-------+--------+---------+

Table 2: Maximum luminosities that can be reached after 3 week ramp-up
period.

Finally, Table 3 shows the expected integrated luminosities per week and
total integrated luminosity for a run with 2 modes ( 7 weeks / mode) and
a run with 3 modes (3 weeks / mode) for both last year's luminosities
(from Table 1), which represents a minimum expectation, and for the
maximum luminosities from Table 2.

+--------+----------+--------+---------+---------+---------+---------+
| Mode   | L~ave~   | Int.   | Int.    | L~ave~  | Int.    | Int.    |
|        | (week)\  | Lumi.  | Lumi.   | (week)\ | Lumi.   | Lumi.   |
|        | \[we     |        |         | \[wee   |         |         |
|        | ek^-1^\] | 2      | 3 modes | k^-1^\] | 2 modes | 3 modes |
|        |          | modes  |         |         |         |         |
+--------+----------+--------+---------+---------+---------+---------+
|        | Minimum  |        |         | Maximum |         |         |
|        | exp      |        |         | expe    |         |         |
|        | ectation |        |         | ctation |         |         |
|        | (from    |        |         | (from   |         |         |
|        | Table 1) |        |         | Table   |         |         |
|        |          |        |         | 2)      |         |         |
+--------+----------+--------+---------+---------+---------+---------+
| Au-Au  | 2        | 168(   | 72      | 70      | 490     | 210     |
|        | 4(b)^-1^ | b)^-1^ | (b)^-1^ | (b)^-1^ | (b)^-1^ | (b)^-1^ |
+--------+----------+--------+---------+---------+---------+---------+
| (p-p)  | 0.3      | 2.1(p  | 0.9(    | 2.8(    | 19.6(   | 8.4(    |
|        | (pb)^-1^ | b)^-1^ | pb)^-1^ | pb)^-1^ | pb)^-1^ | pb)^-1^ |
+--------+----------+--------+---------+---------+---------+---------+
| d-Au   | ?        | ?      | ?       | 4       | 28      | 12      |
|        |          |        |         | (       | (       | (       |
|        |          |        |         | nb)^-1^ | nb)^-1^ | nb)^-1^ |
+--------+----------+--------+---------+---------+---------+---------+
| Si-Si  | ?        | ?      | ?       | 5       | 35      | 15      |
|        |          |        |         | (       | (       | (       |
|        |          |        |         | nb)^-1^ | nb)^-1^ | nb)^-1^ |
+--------+----------+--------+---------+---------+---------+---------+

Table 3: Expected integrated luminosities during the data taking period
for 2 and 3 modes. The first three columns represent the minimum values,
the last three columns show the maximum expected.

All the modes listed will require a similar set-up and ramp-up time of a
total of about 5 weeks. After a running mode has been established
changing the collision energy can be achieved in about 2 weeks ( 1 week
set-up and 1 week ramp-up).

Following are specific comments on the running modes:

**[d-Au:]{.underline}**

d --Au collisions can be set-up with the deuteron beam in either blue or
yellow ring. The present preferred option is with deuterons in the blue
ring if d-Au is the first mode during the upcoming run. This will allow
set-up with deuteron beam to begin earlier since the blue ring is cold a
few days before yellow. Switching to deuterons in the yellow ring at a
later time should be regarded as going to a different mode with again
about 2 weeks of set-up and 3 weeks of ramp-up.

**[pol. protons-pol. protons:]{.underline}**

We expect that the p-p luminosity can be increased significantly since
it should be possible to go to beta-star of 1 m with a working betatron
tune feedback. During the last run p-p was much less sensitive to
intensity related vacuum problems and we therefore expect that operation
with 112 bunches should be possible.

The Siemens motor-generator for the AGS will be repaired and give us
again the nominal ramp rate. Also, the source polarization has been
improved from typically 65-70% to 75%. Based on previous polarized
proton operation with the Siemens this should give about 45 %
polarization at AGS extraction without any further improvements. With
additional improvements, developed during the last run, a polarization
of up to 50-55% could be reached. We are installing a fast polarimeter
in the AGS which is based on the RHIC polarimeter design. This should
significantly improve the reliability of polarization delivery from the
AGS.

We are proposing that a RHIC p-p run is scheduled later during the RHIC
run so that a 3 week AGS polarized proton commissioning run can be
completed before a RHIC p-p run would start. The goal of this
commissioning run would be to demonstrate a minimum of 45% polarization
at AGS extraction.

A first test of acceleration of polarized protons to 250 GeV in RHIC
would be very useful to prepare for future running. With the RHIC tune
feedback and a resurveyed machine it is expected that polarization would
survive to full energy.

**[Au-Au:]{.underline}**

The main improvement for Au-Au operation will come from improved vacuum
bake-out and low field solenoids in the warm sections to suppress
intensity related instabilities. We are hoping to reach full design
intensity. At the same time we are installing instrumentation to be able
to investigate this instability.

**[Si-Si:]{.underline}**

The listing for Si-Si serves as an example of an intermediate heavy ion.
Si is easily produced by the injector and with an equal number of
protons and neutrons acceleration in RHIC is the same as for deuterons.