Closing ionic popup after some time : Removes popup styles when it is shown next time

Question

I am using AngularJS, ionic1. I have some functionality in my app which runs after certain time and shows a success popup. I am using $ionicPopup.alert for this. When close popup after certain time it is perfectly working fine, but it removes popup styles when it is shown next time.
Here is my test code:

 $ionicPopup.alert({
                     title: 'Operation Successful',
                     template: 'operation has been completed'
                     });

$rootScope.promise_closePopup;
$rootScope.promise_closePopup = $interval($rootScope.closePopup, 9000);

and for closing popup:

 $rootScope.closePopup = function () {
        var popuplist = $ionicPopup._popupStack;
        if (popuplist.length > 0) {
            popuplist.forEach(function (popup, index) {   
                popup.remove();
                popuplist.pop();
            });
            $ionicBackdrop.release();
            $ionicBody.removeClass('popup-open');
            $interval.cancel($rootScope.promise_closePopup);
        }
    };