Resonant mass

detectorsPia Astone

4th Amaldi conference

Perth July 8-13, 2001

….these early experimentsinitiated research

into gravitational waves experiments that is still ongoing.

Current g.w. experiments aredescendants of Weber’s

original work

M ; T ; Q

The Eq of geodetic deviation is the basis for all the experiments to detect g.w.

Thermal noise, T=300mK, L=3 10-18 m

They play a rolethat is similar to

L ; P ; Ffor interferometers

Main characteristics of the detectors

ALLEGRO: 2300 kg, Al antenna,The two resonance frequencies are 897 and 920 Hz.

Cooled at 4.2KOperational since 1991

IT IS IN BATON ROUGE, LOUISIANA (U.S.A.)

AURIGA: 2230 kg, Al antennaCooled at 200 mK, with a liquid helium dilution refrigerator

The two resonance frequencies are 921 and 930 Hz Operational since 1997

IT IS IN LEGNARO (PADOVA)

Explorer : 2270 kg, Al antennaCooled at 2.6 K

The two resonance frequencies are 888 and 919 Hz Operational since 1990

IT IS AT CERNNAUTILUS: 2260 kg, Al antenna

Cooled at 130 mK, with a liquid helium dilution refrigerator

The two resonance frequencies are 905 and 924 Hz Operational since Dec. 1995

IT IS IN FRASCATI (ROME)

Niobe: 1500 kg, Niobium antennaCooled at 5 K.

The two resonance frequencies are 694 and 713 HzOperational since 1993

IT IS HERE

The expected signal h is a short pulse ( a few ms).

Bars can look for:

The expected value on Earth,

if 1% of Mo is converted into g.w. in the GC,

is of the order of 10-18

Bursts

Two collapsed objects ( 2 neutron stars, 2 black holes, one of each) , that orbit each other at close range and high orbital frequency.Amplitude and frequency increase with time, until the final merge.

h

Time[s]

h

Bars can look for:

Chirp

Bars can look for:

Signals from rotating neutron stars, stars in binary systems

Continuous signals

Noise, produced from a high number of

uncorrelated events

Cosmological origin: it is the result of processes that happened immediately after the Big-Bang. If measured, it will allow to discriminate various cosmological models

Astrophysical origin: it is the result of more recent event (redshift z order of 2-5). It is due to unresolved processes of gravitational collapses. It will provide information on star formation rates, supernova rates, black holes......

Bars can look for:Stochastic background

AN EXAMPLE OF STRAIN SENSITIVITYof a resonant g.w. detector

NAUTILUS1999

Sqrt(T/MQ)Note that

the bandwidth depends ONLY on thetransducer and amplifier

Calibrationsignal

659 d

553 d

852 d

221 d

200 d

ON times for the various detectors 1997-2001

THE ALLEGRO DETECTOR IS VERYSTATIONARY AND HAS A VERY

HIGH DUTY CYCLE

Tobs=328 days !!

h=1*10-18

ALLEGRO 1998

Talk by S. Heng

The AURIGA sensitivity (first run 97-99)

July, 1999

h=2.5 10-19

4 10-22 /sqrt(Hz)B=6 Hz

Talk by A. Ortolan

Explorer , Nautilus and Niobe are now working with a

sensitivity of h=4-5*10-19

1-14 June 2001

h=4*10-19

h=7*10-19

Talks by Visco, Coccia, Blair

NEWS on the detectors

ALLEGRO: It has been relocated and will be again on the air in a few weeks.

(2.0 *10-21 /sqrt(Hz), B= 1 Hz)Next:

It will be equipped with a new 2-mode transducer and with a Wellstood SQUID amplifier.

The expected bandwidth is 60 Hz,and the expected strain sensitivity

1 *10-21/sqrt(Hz)

AURIGA: A new readout (new double stage SQUID, new tranducer) is being tested.

New mechanical suspensions (360 dB @1kHz). The system will be operative before

the end of this year. The expected strain sensitivity is

6*10-22/sqrt(Hz) B=40 Hz @1*10-21/sqrt(Hz) Phase I (2001)

2*10-22 /sqrt(Hz) B=80 Hz @1*10-21/sqrt(Hz) Phase II (2002)

Explorer : the tranducer and the SQUID have been replaced . This year:

increase the Q of the transducer to increase the strain sensitivity.

Work on the SQUID (to reduce extra noise)We expect a bandwidth of 30 Hz @ 3*10-21 /sqrt(Hz);

Next year: Install cosmic ray detectors around the bar

NAUTILUS: after the summer the bar will be replaced and the new system will work at 935 Hz;

A new transducer and SQUID (the same used for Explorer)

will be used(to increase the sensitivity)

We expect: 6*10-23 /sqrt(Hz) @935 Hz

Niobe: it has been cooled down again in Feb. 2001.The readout system has been improved, to increasethe sensitivity (new low noise micro wave amplifier)

The antenna has been equipped with cosmic ray detectors

(Univ. of Adelaide osmic ray detector array)

Explorer strain sensitivity(2000-2001)

But the system was not stable in

this situationAND..

10-21 /sqrt(Hz)

10-20 /sqrt(Hz)

880 890 900 910 920 930 940 95010

-21

10-20

10-19

10-18

frequency (Hz)

GW

spe

ctra

l am

plitu

de (

h/rt

(Hz)

)

present condition

increasing Q and

decreasing electronic

noise

decreasing electronic

noise

Explorer strain sensitivity

10-21

10-20

1/sqrt(Hz)

3 10-21

GOAL for this year :

Sh=(1 10-21 /sqrt(Hz))2

B=30 Hz @ 3 10-21 /sqrt(Hz)

Calibration

The expected AURIGA strain sensitivity:Phase I (2001)

Operating Temperature 1.5 KSh=(6 10-22 /sqrt(Hz))2

B=40 Hz @ 1 10-21 /sqrt(Hz)

h=1.3 10-19(burst)

Phase II (2002)Operating Temperature 100 mK

Sh=(2 10-22 /sqrt(Hz))2 B=80 Hz @ 1 10-21 /sqrt(Hz)

h=5 10-20(burst)

Talk by J.P. Zendri; Posters by Vinante, Marin

Optical readout for AURIGA

• Bar motion read by FP cavity, mounted between the bar and the resonant transducer

• May 2001: the system has been operating on a room temperature bar, in Legnaro (10 days)

10-20 /sqrt(Hz)

10-19 /sqrt(Hz)

820 940 Talk by M. De Rosa

Next steps:Underst. agreement with model

Test optomechanical parts atlow temperature

Develop and test a cryogenic prototype

NAUTILUS at 935 Hz (after the summer): expected strain sensitivity with the new transducer

10-2210-22

10-20

10-21

870 970Hz

1/sqrt(Hz)

6*10-23/sqr(Hz)

@935 Hz

840 Hz 980

http://igec.lnl.infn.it

554 d

416 d

852 d

221 d

186 d

ON times for the various detectors 1997-2000

Results of the First Analysis(1997-1998 data, old protocol)

No detection of g.w. bursts above

That is no events which converted 0.07 solar masses in the Galaxy

h=4 x 10 -18

Discussion for IGEC:refer to the talk of G. Prodi

at this conference

Net observation times(1997-2000 data-New protocol)

• 1 detector: 1322 (past:625) days

• 2 detectors: 713 (past:260) days

• 3 detectors: 178 (past: 90) days

• 4 detectors: 29 (past: 16) days

• 5 detectors: 0 (past: 0) days

The total span of the time of the analysis is 4 years=1460 daysIn case of an astronomical trigger, the time coverage is 90%, over 4 years

Search for bursts-what we plan to do-

• Analysis of the 1997-2000 IGEC data (new protocol more information). New algorithms.

• We are preparing for future analysis in collaboration with interferometers : 1) use of Frames 2) study of the problem (waveforms versus detector’s bandwidth)

The use of FRAMES for the AURIGA detector:see the poster of Gabriele Vedovato

Optimum filters for bursts: see the poster of Sabrina D’ Antonio

EXPLORER and NAUTILUS Feb. 1997

Crosscorrelation measurement of stochastic g.w. background with two resonant detectors

(Astr. Astroph 351,1999)

(see also Phys. Lett. B, 385, 1996)

12 hours of data

Bandw.=0.1 Hz

Omega_gw

< 6*10

10-42

10-38

10-40

Sh Hz-1

905 925 Hz

Stochastic g.w. background-what we plan to do-

• New limit using AURIGA I and NAUTILUS:

with t_obs=4 month;

ShN=(6*10-23- 1*10-22)2 1/Hz ; ShA=(1*10-21 )2 1/Hz @935 Hz

Omega_gw=10-1, Df=1 Hz Year 2002

(a factor 2 better if AURIGA is tuned at 935 Hz)

. Joint analysis with Virgo (ShV=(1*10-22)2 1/Hz @ 900 Hz):

Virgo – AURIGA II: 3*10 –3 (1 year, Df=80 Hz)

Virgo – NAUTILUS: 5*10 –3 (1 year, Df= 1 Hz) (and also: Virgo-AURIGA-NAUTILUS).

S. Vitale et al. Phys. Rev D, 55,1997;Maggiore Phys Rep. 331.6 ,2000

• Joint analysis with LIGO. LIGO–ALLEGRO : 10-1 - 6*10 –4 ( 40 km apart) S. Finn, A. Lazzarini grqc0104040 (2001)

0.1 is obtained using LIGO I

(h(f)=10-22 1/sqrt(Hz) at 1kHz )

the present ALLEGRO (h(f)=2*10-21 1/sqrt(Hz))

1 year (analysis done at pieces of 2-3 months)

and a bandwodth of 1 Hz

3*10-4 is obtained using LIGO II

(h(f)=10-23 1/sqrt(Hz) at 1kHz)

Improved ALLEGRO h(f)=10-22 1/sqrt(Hz)

1 year (analysis done at pieces of 2-3 months)

and a bandwodth of 50 Hz

=0.1 can be obtained using LIGO I

(h(f)=10-22 1/sqrt(Hz) at 1kHz )

the present ALLEGRO (h(f)=2*10-21 1/sqrt(Hz))

1 year (analysis done with periods of 2-3 months)

and a bandwidth of 1 Hz

=6*10-4 is obtained using LIGO II

(h(f)=10-23 1/sqrt(Hz) at 1kHz)

Improved ALLEGRO h(f)= 1 10-21 1/sqrt(Hz)

1 year (analysis done with periods of 2-3 months)

and a bandwidth of 60 Hz

Continuous wave analysis

• Limits for signals in the GC and Tucanae has been obtained using 3 months of ALLEGRO 1994 data, at a level of the order of

hc=5*10 –24 (Hamilton, Pr. of the 2nd E. Amaldi1997)

• Limit for signals in the GC, using 95 days of Explorer data

hc=3*10 –24 (ROG+Frasca+ Papa, subm to PRD, 2001)

Continuous wave analysis

• Overall sky search (2 days,Df=0.8Hz) of data is now running and will end by the summer: the analysis will put limits at the level of

hc=3*10 –23 (the procedure is in Astone, Borkowsky, Jaranowsky, Krolak, gr-qc/0012108 subm. to PRD,2001)

• Incoherent analysis over 1 year of data of Explorer 1991 (Astone,Krolak,Rog coll:”A fast search for continuous g.w. signals”…we are writing the paper

• Extend the analysis to 1997-2000 data

So far we have done random search of the parameter space for 1 million points.

We choose a threshold for SNR of 6.6. We haveobtained 123 thr. crossing. Each event is verified bytwo matched filters with the parameters of the event.

See the Krolak’ s talk at the GR16

We will use the Rome strategy for thepulsar search, developped for Virgo

(Frasca,Palomba,Ricciand the ROG collaboration)

Use of the NAUTILUS data at 935 Hz to search for the neutron star in the SN1987A

Sh=(6 10-23 /sqrt(Hz))2

tobs=1 year

h0=sqrt(2 Sh / t_obs)=1.5 10-26

The signal :P=2.14 ms, dP/dt=2 10-10 Hz/s

The estimation of oblateness is order of 10-6 h of order 10-26

(Middleditch et al., New Astronomy, 5, 243, 2000)

AURIGAPhase I or Phase II with the bar at 935:

Sh=6-2 10-22 /sqrt(Hz)

h0=sqrt(2 Sh / t_obs)=( 15 – 5 ) 10-26

A new activity

Spherical detectors

a sphere has 5modes of vibrationinteracting strongly

with a g.w.Each mode can act asa separate antenna,oriented towards a

different polarizationor direction

SMALL SPHERICAL DETECTORSin preparation

Material=Cu AlDiameter=65 cm

Mass=1 tonFrequency=3 kHz

Brazil: Mario Shenberg

The Netherlands: Mini GRAIL

Italy: Sfera

Mini GRAIL

Gravitational waves are a tool for astronomical observations “they can reveal features of their sources

which no one could ever learn by electromagnetic

or neutrino studies”

Kip Thorne

The Nautilus g.w. detector andthe interaction with cosmic rays

• Thermo-acustical model of interaction of cosmic rays with a bar detector (Liu-Barish, De Rujula, Cabibbo, Amaldi-Pizzella)

• “Expected” result for low-amplitude signals October 98-Jan 99 (Phys. Rev Lett. 84, Jan 2000)

• “Unexpected” result for high-amplitude signals (Phys. Lett. B 499, Jan 2001)

E = 57.89 K. 87 TeV.

The value of the merit factor, estimated from the signal, is Q = 1.7 105.

Unfiltered signal (V2)

The signal after the filtering (kelvin)

The biggest event observed has E=58 K(the energy released in the bar is 87 TeV)

The problem is very interesting, as itinvolves:

gravitational waves, cosmic rays,particle detection,

low temperature physics

1) Analysis of the data obtained with NAUTILUS at 1 K

2) Cosmic ray detectors will be installed around Explorer

Refer to the talk of F. Ronga at this meeting

3)Cosmic ray detectors have been putaround Niobe (different superconducting

material)

CONCLUSIONS

We have many interestingimprovements and analyses to do

The collaboration within the entireg.w. community is

essentialfor the exploration of thisnew frontier of kwnoledge

Dato il tasso di aspettazione di EAS al livello del mare [5]: ( = noparicelle cariche/m2)

4 (1.32 0.038ln )( ) 3.54 10EAS

Hday

[5]G. Cocconi, Encyclopedia of Physics Vol.46 p.228 (Publisher, City, 1961)

1 energia media attesa per un evento con molteplicità maggiore di M

E energia media misurata

Sensitivity to continuous waves

hc= sqrt(Sh/t_obs) if the source is known

hc

Ground based detectors and Pulsar Sources

1 year1 year

IGEC DETECTORS

The detector sensitivity to the various signals:

• Burst h: Sh, Df ; matched filters ; coincidences between 2 or more detectors

• Continuous sources hc: Sh, t_obs ; only one detector; Fourier analysis, pattern tracking

• Stochastic background _gw: Sh1, Sh2(h), Df , t_obs ; crosscorr. 2 or more detectors

A rotating neutron star:

It will emit g.w. if the mass distribution is non axis-simmetric along the rotation axis.

About 109 NEUTRON STARS are expected to exist in the Galaxy, but

only ~ 1000 have been detected, most as PULSARS.

The expected AURIGA strain sensitivity

h=1 10-20(burst)

Sh=(1 10-22 /sqrt(Hz))2 B=50 Hz

NEWS on the detectors

ALLEGRO: It has been relocated and will be again on the air in a few weeks.

Next:It will be equipped with a new transducer

and with a new SQUID amplifier.The expected bandwidth is 50 Hz,

and the expected gain in strain sensitivity a factor of 10

( 1 *10-22/sqrt(Hz) )

AURIGA: A new readout (new capacitive tranducer and new SQUID)

is being tested. The system will be operative after the summer

The expected bandwidth is 50 Hz and the expected gain in strain sensitivity is a factor 4

( 1*10-22/sqrt(Hz) )

Explorer : the tranducer and the SQUID have been replaced . Now the bandwidth is 50 Hz @ 5*10-21 /sqrt(Hz);

Next year: increase the Q of the transducer to increase the

strain sensitivity.Install cosmic ray detectors around the bar

NAUTILUS: after the summer the bar will be replaced and the new system will work at 935 Hz;

A new transducer and SQUID (the same used for Explorer)

will be used(to increase bandwidth and sensitivity)

Niobe: it has been cooled down again in Feb. 2001.The readout system has been improved, to increase

the sensitivityThe antenna has been equipped

with cosmic ray detectors

0.1 is obtained using LIGO I

(h(f)=10-22 1/sqrt(Hz) at 1kHz )

the present ALLEGRO (h(f)=2*10-21 1/sqrt(Hz))

1 year (analysis done at pieces of 2-3 months)

and a bandwodth of 1 Hz

3*10-4 is obtained using LIGO II

(h(f)=10-23 1/sqrt(Hz) at 1kHz)

Improved ALLEGRO h(f)=10-22 1/sqrt(Hz)

1 year (analysis done at pieces of 2-3 months)

and a bandwodth of 50 Hz

=0.1 can be obtained using LIGO I

(h(f)=10-22 1/sqrt(Hz) at 1kHz )

the present ALLEGRO (h(f)=2*10-21 1/sqrt(Hz))

1 year (analysis done with periods of 2-3 months)

and a bandwidth of 1 Hz

=3*10-4 is obtained using LIGO II

(h(f)=10-23 1/sqrt(Hz) at 1kHz)

Improved ALLEGRO h(f)=10-22 1/sqrt(Hz)

1 year (analysis done with periods of 2-3 months)

and a bandwidth of 50 Hz

NEWS on the detectors

ALLEGRO: It has been relocated and will be again on the air in a few weeks.

(2.0 *10-21 /sqrt(Hz), B= 1 Hz)Next:

It will be equipped with a new 2-mode transducer and with a Wellstood SQUID amplifier.

The expected bandwidth is 60 Hz,and the expected strain sensitivity

1 *10-21/sqrt(Hz)

AURIGA: A new readout (new double stage SQUID, new tranducer) is being tested.

New mechanical suspensions (360 dB @1kHz). The system will be operative before

the end of this year. The expected strain sensitivity is

6*10-22/sqrt(Hz) B=40 Hz @10-21/sqrt(Hz) Phase I (2001)

2*10-22 /sqrt(Hz) B=80 Hz @10-21/sqrt(Hz) Phase II (2002)

Explorer : the tranducer and the SQUID have been replaced . Now the bandwidth is 50 Hz @ 5*10-21 /sqrt(Hz);

Next year: increase the Q of the transducer to increase the

strain sensitivity.Install cosmic ray detectors around the bar

NAUTILUS: after the summer the bar will be replaced and the new system will work at 935 Hz;

A new transducer and SQUID (the same used for Explorer)

will be used(to increase the sensitivity)

Niobe: it has been cooled down again in Feb. 2001.The readout system has been improved, to increasethe sensitivity (new low noise micro wave amplifier)

The antenna has been equipped with cosmic ray detectors

(Univ. of Adelaide osmic ray detector array)

NAUTILUS: expected strain sensitivity with the new transducer

App. Phys Lett. 72,115 (1998)

dcSQUID

10-2210-22

10-20

10-21

870 970Hz

1/sqrt(Hz)

Net observation times(1997-1998 data-old protocol)

• 1 detector: 625 days

• 2 detectors: 260 days

• 3 detectors: 90 days

• 4 detectors: 16 days

• 5 detectors: 0 days

The total span of the time of this first analysis is 2 years=730 days