Checkbox checked, disabled it

Please, will you help me?

I need disable a checkbox with javascript after it has been selected, I did the next :

I selected a rows from Postgres DB for create the checkbox. I use a Perl languaje in Linux Centos 7, the code is next:

while(my $ref_alarm = $sth->fetchrow_hashref()) {

        ($gabinete)=$ref_alarm->{'gabinete'};

        ($alarma)=$ref_alarm->{'descrip_alarma'};

        print "<input type='checkbox' name='alarma' id='alarma' value='$alarma' onclick='alarma_reg(this.value);'/>$alarma</input>";

        print "<br>";

}

I had been use javascript for disable the checkbox that had been selected:

function alarma_reg(p_alarma) {

                //Get the checkbox

                document.getElementById("p_alarma").disabled = true;

                alarma_operada+=p_alarma + ',';

                document.getElementById("ver_alarmas").value=alarma_operada;

        }

But the option selected is not disable, please could you help me?

Regards

Xochitl